Non-malignant skin disease

Non-malignant skin disease is relatively common. The pathology may or may not be specific. Some diseases require clinical information to diagnose.

An introduction to dermatopathology is in the dermatopathology article. Nevi (moles) and other melanocytic lesions are dealt with in the article melanocytic lesions. Inflammatory skin conditions are dealt with in inflammatory skin disorders.

Other

Lichen simplex chronicus

• Abbreviated LSC.
• AKA squamous cell hyperplasia.

General

• May be considered a variant of spongiotic dermatitis.; more specifically, some think it is an atopic dermatitis (which fits in the large spongiotic dermatitis category).
• It is lumped with the psoriasiform dermatitides.

Etiology:

• Pruritus (itchness) -> mechanical trauma -> lichenification (thickened/leathery.

Microscopic

Features:

• Acanthosis (epithelial thickening) - irregular.
• Hyperkeratosis.

Other features:

• Spongiosis (epidermal intercellular edema -- cells appear to have a clear halo around 'em).
• Parakeratosis = retention of nuclei in the stratum corneum.

DDx:

• Prurigo nodularis - focal process (nodule or papule).
• Benign alveolar ridge keratosis (AKA oral lichen simplex chronicus) - see oral pathology.

Images:

• LSC - low mag. (WC).
• LSC - high mag. (WC).

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SKIN, PUNCH BIOPSY:
- LICHEN SIMPLEX CHRONICUS.
- NEGATIVE FOR MALIGNANCY.

Oral

RETROMOLAR PAD, RIGHT, PUNCH BIOPSY:
- ORAL LICHEN SIMPLEX CHRONICUS.
- NEGATIVE FOR MALIGNANCY.

Micro

The sections show a squamous mucosa with irregular psoriasiform change, parakeratosis, and focal hypergranulosis. There is no inflammation at the interface. Epidermal intercellular bridges are easily seen. There is no significant nuclear atypia. Mitoses are not evident.

Prurigo nodularis

• Abbreviated PN.
• AKA chronic prurigo and picker nodule.

General

• Can be thought of as a localized/focal version of lichen simplex chronicus (LSC).

Gross

• Dome-shaped/raised - papular (<1 cm) or nodular (>1 cm).

Microscopic

• See lichen simplex chronicus.

DDx:

• Lichen simplex chronicus - a more diffuse process, not a raised lesion.

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SKIN LESION, LEFT CHIN, BIOPSY: 
- PRURIGO NODULARIS.

Micro

The sections show a raised lesion with compact hyperkeratosis and irregular acanthosis. Spongiosis is seen focally. There is minimal hypergranulosis.

There is no thinning of the suprapapillary plate and no dilated superficial blood vessels. There is no interface activity.

Very common

Dermatomycosis

Dermatophytosis redirects here.

General

• Fungal infection of skin.

Note:

• Dermatophytosis (ring worm) is a type of dermatomycosis.

Microscopic

Features:

• Microorganisms - key feature.
  • Often hyphae (candida) - like twigs of a tree... branching.
    • May be very fragmented in section ~ size of a neutrophil.
• Perivascular inflammation, esp. neutrophils.
• Exocytosis - blood cell infiltrate the epidermis.

Images:

• WC:
  • Dermatomycosis - intermed. mag. (WC).
  • Dermatomycosis - high mag. (WC).
  • Dermatomycosis - GMS stain - low mag. (WC).
  • Dermatomycosis - GMS stain - high mag. (WC).
• www:
  • Dermatophytosis (ucsf.edu).

Stains

• GMS stain.
• PAS-D stain.

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SKIN, BIOPSY:
- SKIN WITH SUPERFICIAL FUNGAL ORGANISMS CONSISTENT WITH CANDIDA.
- REACTIVE CHANGES OF THE EPITHELIUM.

Micro

The sections show skin with a neutrophilic infiltrate in the superficial epidermis. PAS-D staining demonstrates fungal organisms with a morphology suggestive of candida.

The epithelium has parakeratosis, acanthosis and spongiosis. No mitotic activity is appreciated. The keratinocytes are moderately enlarged and have evident nucleoli.

Cicatrix

• AKA scar, dermal scar.

General

• Previous surgery, biopsy, trauma.

Microscopic

Features:

• Loss of dermal papilla.
• Dense collagen - fibers run parallel to the dermal-epidermal (DE) junction - key feature.
• Loss of adnexal structures.

Other feature:

• Thin-walled blood vessels.
  • Described as running perpendicular to the surface - this may not be apparent.

Note:

• There should not be any nuclear hyperchromasia or pleomorphism.

DDx:

• Malignant melanoma, desmoplastic-neurotropic type - nuclear pleomorphism and/or hyperchromasia; may be focal.
• Dermatofibroma.
• Desmoplastic Spitz nevus.
• Sclerosing blue nevus.

Image:

• Scar (WC).

IHC

• S100 focal/scattered +ve.
  • Desmoplastic melanoma strong +ve.
• HMB-45 -ve.
  • Sclerosing blue nevus +ve.

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SKIN, LOWER MID BACK, RE-EXCISION:
- DERMAL SCAR.
- SOLAR ELASTOSIS.

Micro

The sections show skin with a dermis with dense collagen fibres that run parallel to the skin surface without adnexal structures. The overlying dermal-epidermis interface lacks the typical undulation.

Fibroepithelial polyp

• AKA acrochordon.
• AKA skin tag.

General

• Benign.
• Older people.
• May be associated with pregnancy, diabetes, intestinal polyposis.
• Can be a component of Birt–Hogg–Dubé syndrome.

Gross

• Raised skin-coloured lesion.

Image:

• Skin tag (WC).

Microscopic

Features:

• On a stalk / epithelium on three sides.
• Benign epidermis.

DDx:

• Pedunculated seborrheic keratosis - typically have epidermal hyperplasia, hyperkeratosis, horn cysts.
• Regressing melanocytic lesions.
  • Intradermal melanocytic nevus.
• Nevus lipomatosus superficialis - abundant adipocytes in the superficial dermis.
• Neurofibroma.

Images:

• Fibroepithelial polyp (dermatlas.med.jhmi.edu).
• Fibroepithelial polyp (surgicalpathologyatlas.com).
• Inflamed fibroepithelial polyp (cdlib.org).

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SKIN ("SKIN TAG"), THIGH, EXCISION:
- FIBROEPITHELIAL POLYP.

Micro

The sections show a fragment of skin with epithelium on three sides. The epithelium matures and is not hypertrophic. Orthokeratosis is present. The core of the lesion has fibrous tissue. There is no significant inflammation. No melanocytic nests are identified.

Inflamed

The sections show a fragment of skin with epithelium on three sides. The epithelium matures and is acanthotic. Minimal parakeratosis is present. The core of the lesion consists of fibrous tissue with a mild lymphocyte-predominant dermal infiltrate. Rare siderophages are present.

There is mild basal nuclear enlargement. No significant nuclear atypia is apparent. The dermal-epidermal interface is well-demarcated. Rare basal mitotic activity is identified.

Actinic keratosis

Bowenoid actinic keratosis redirects to here.

• Abbreviated AK.
• AKA solar keratosis.

General

• Considered a precursor of squamous cell carcinoma of the skin.

Risk factors:

• Sun exposure.
• Immune suppression (e.g. organ transplant recipients).

Gross

Features:

• Yellow-brown scaly, patches.
• Sandpaper sensation - on touching.
• May be pigmented.

Microscopic

Features:

• Epidermal nuclear atypia:
  • Variation is size, shape and staining - must involve basilar layer.
    • Nuclear enlargement - key feature.
    • Hyperchromasia.
• Abnormal epidermal architecture:
  • Palisading.^{[citation needed]}
• +/-Parakeratosis - may alternate with orthokeratosis, esp. early lesions.
• +/-Irregular acanthosis.

Note:

• May be full thickness - known as bowenoid actinic keratosis.

DDx:

• Actinic cheilitis - the same lesion on the lip.
• Bowen's disease - full thickness involvement - with involvement of adnexal epithelium and follicular epithelium.
• Paget disease of the breast.
• Squamous cell carcinoma of the skin.
• Lentigo maligna (melanoma in situ on sun damaged skin) - esp. for pigmented AK.
• Seborrheic keratosis - should not have basilar nuclear atypia.

Images:

• Actinic keratosis (WC).
• Actinic keratosis (WC).
• Actinic keartosis (WC).
• Bowenoid actinic keratosis - high mag. (WC).
• Bowenoid actinic keratosis - very high mag. (WC).

Histologic subtypes of actinic keratosis

Like most common things, there are several variants:

• Hypertrophic actinic keratosis.
  • Increased thickness of: (1) epidermis and, (2) stratum corneum.
• Acantholytic actinic keratosis.
• Proliferative actinic keratosis - downward finger-like projections of the epidermis.
• Pigmented actinic keratosis.
  • DDx: lentigo maligna.
• Lichenoid actinic keratosis.

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SKIN LESION, RIGHT THIGH, BIOPSY:
- HYPERTROPHIC ACTINIC KERATOSIS.
- SOLAR ELASTOSIS.
- NEGATIVE FOR MALIGNANCY.

Bowenoid

SKIN LESION, RIGHT DISTAL FOREARM, BIOPSY:
- BOWENOID ACTINIC KERATOSIS, COMPLETELY EXCISED IN PLANE OF SECTION.
- EXTENSIVE SOLAR ELASTOSIS.
- NEGATIVE FOR MALIGNANCY.

Micro

General

The sections show skin with basilar epidermal nuclear enlargement and hyperchromasia with irregular nuclear palisading. Hyperkeratosis and parakeratosis is present. A granular layer is present. The dermal-epidermal interface is sharply-demarcated. There is focal inflammation at the interface. Extensive solar elastosis is present.

There is no clefting of the lesion from the surrounding stroma. The surrounding stroma does not have a myxoid quality.

Bowenoid

The sections show skin with epidermal nuclear enlargement and hyperchromasia with irregular nuclear palisading. The lesion involves the full thickness of the epidermis; however, it spares adnexal and follicular epithelium. Proliferative activity is present. Hyperkeratosis and parakeratosis is present. A granular layer is present. The dermal-epidermal interface is sharply-demarcated. There is focal inflammation at the interface. Extensive solar elastosis is present.

There is no clefting of the lesion from the surrounding stroma. Intercellular bridges are identified.

Actinic cheilitis

General

• Actinic keratosis of the lip.

Microscopic

See actinic keratosis.

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LESION, LOWER LIP, BIOPSY: 
- ACTINIC CHEILITIS.
- SOLAR ELASTOSIS.

Micro

The sections show skin with moderate basal nuclear hyperchromasia and atypia, and parakeratosis. The squamous epithelium has maturation to the surface. There is no inflammation at the dermal-epidermal interface. Solar elastosis is present.

Seborrheic keratosis

• Abbreviated SK.

General

• Benign.
• Most common tumour in older people.
• "Large number" of SKs = paraneoplastic syndrome (Leser–Trélat sign).

Epidemiology:

• Old people.
• Usually in sun exposed area.

Gross

• "Stuck-on" appearance - raised lesion.

Image(s):

• SK - gross image (dermatlas.org).

Microscopic

Features:

• Raised above skin surface.
• Border sharply demarcated.
• Hyperkeratosis - stratum corneum extra thick.
  • May be minimal.
• Horn cysts - intraepidermal collections of keratin - key feature.
  • Actually invaginations - not true cysts; thus, they may more accurately be called pseudohorn cysts.
• Clusters of cells with brown granular material in the superficial dermis/dermoepidermal junction - pigmented melanocytes.

DDx:

• Actinic keratosis - especially, irritated SKs; have nuclear atypia and parakeratosis.
• Verruca vulgaris - SK may have papillomatous projections.
• Basal cell carcinoma, fibroepitheliomatous pattern - esp. reticulated SK.
• Melanocytic nevus.
• Condyloma acuminatum - may have horn cysts, more probable than SK in the genital area.
• Inverted follicular keratosis - predominantly endophytic growth pattern, may be considered a variant of seborrheic keratosis.

Images:

• Seborrheic keratosis - low mag. (WC).
• Seborrheic keratosis - high mag. (WC).
• Seborrheic keratosis - high mag. (dermatlas.org).
• Seborrheic keratosis - low mag. (dermatlas.org).

Histologic subtypes

Like very common lesion, there are subtypes:

• Acanthotic seborrheic keratosis - thickened stratum spinosum; thick epidermis.
• Reticulated seborrheic keratosis - vaguely resembles fibroepithelioma of Pinkus (BCC, fibroepitheliomatous pattern).
• Irritated seborrheic keratosis - spongiosis (epidermal intercellular edema) and inflammation.
• Digitated seborrheic keratosis - papillomatous projections, architecture mimics a verruca.
• Stucco keratosis - pointed papillomatous projections.

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SKIN LESION, MID BACK, BIOPSY:
- SEBORRHEIC KERATOSIS.

Micro

The sections show skin with acanthosis, pseudohorn cysts, parakeratosis, hyperkeratosis and focal basal epidermal pigmentation. There is no basal nuclear atypia, no mitoses and there are no melanocytic nests. There is minimal dermal inflammation. There is no solar elastosis.

Without horn pseudocysts

The sections show skin with acanthosis, a thin layer of compact keratin and focal basal epidermal pigmentation. Dilated blood vessels surrounded by collagen are seen in the superficial dermis. No pseudohorn cysts are identified. A granular layer is present.

There is no basal nuclear atypia. There is no mitotic activity and no melanocytic nests. There is no solar elastosis. No koilocytes are apparent.

Minimal hyperkeratosis

The sections show skin with acanthosis, pseudohorn cysts, rare parakeratosis, minimal hyperkeratosis and focal basal epidermal pigmentation. There is no basal nuclear atypia, no appreciable mitotic activity and there are no melanocytic nests. There is minimal dermal inflammation. Solar elastosis is present.

Pilomatricoma

• AKA calcifying epithelioma of Malherbe, AKA pilomatrixoma.

General

• Benign skin tumour.
• Most common solid skin tumour of children.
• CTNNB1 gene mutation important in pathogenesis.

Clinical:

• Hard nodule - calcification.
• +/-Painful.

Treatment:

• Surgical excision.

Microscopic

Features:

• Nodular circumscribed lower dermis/subcutaneous adipose lesion; thus, usu. surrounded by connective tissue.
  • Sharpy demarcated island of cells.
  • Calcification in 75%.
• Cells:
  • Basaloid epithelial cells - have prominent nucleoli.
  • Anucleate squamous cells ("ghost cells").
  • Giant cell foreign body type granulomas (form in reaction to keratin).

Notes:

• Keratin a prominent feature on cytology - lots of orange stuff.
• May ossify.

Images:

• Pilomatrixoma - cytology (bccancer.bc.ca).
• Pilomatrixoma - histology (dermrounds.com).
• Pilomatrixoma - high mag. (WC).
• Pilomatrixoma - intermed. mag. (WC).

DDx:

• Epidermal inclusion cyst.
• Pilomatrix carcinoma - invasive border, cytologic atypia, necrosis.
• Squamous cell carcinoma.
• Basal cell carcinoma.

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SKIN LESION, RIGHT ARM, EXCISION:
- PILOMATRICOMA.

Dermatofibroma

• Abbreviated DF.

General

• AKA fibrous histiocytoma.
• Reactive process -- it is not a neoplasm.
• Usually associated with previous trauma.
  • In women... usually legs.

Microscopic

Features:

• Prominent fibrous bundles, especially at the edge of the lesion.
  • Surrounded by spindle cells (fibroblasts).
    • Usually thought of as fibroblasts surrounded by fibrous material ("collagen-trapping").
• Lack of adnexal structures, i.e. no sweat glands, no hair.
• +/-Epidermal changes - known as "dirty fingers":
  • Acanthosis (thickened epithelial layer - specifically thickened stratum spinosum).
  • Basal keratinocyte hyperpigmentation.

DDx:

• Dermatofibrosarcoma protuberans (DFSP) - usu. deeper, classically has adnexal structures and fat within lesion.
• Neurofibroma.
• Blue nevus.
• Melanoma, esp. desmoplastic neurotropic-type.
• Fibromatosis.

Images:

• Dermatofibroma (ucsf.edu).
• DF - several images (pacificderm.org).
• DF stained with factor XIIIa (biocare.net).

Subtypes

Like all common things... there are subtypes:

• Cellular.
• Deep penetrating.
• Lipidized - with foamy macrophages, hemorrhage and Touton-like giant cells.
• Epithelioid cell histiocytoma.
• Fibrotic.
• Aneurysmal - large blood filled + features of lipidized.
• Granular cell dermatofibroma.
• Dermatofibroma with monster cells.

Cellular dermatofibroma

Features:

• High cell density in the dermis - "blue" at low power.
• Collagen bundles - key feature.

Images:

• Cellular dermatofibroma (surgicalpathologyatlas.com).
• Cellular dermatofibroma (dermpedia.org).

IHC

Features:

• Factor XIIIa +ve.
  • Usually negative in DFSP.
• CD34 -ve.
  • Usually positive in DFSP.

Others:

• D2-40 +ve.
  • Usually negative in DFSP.
  • There is not much literature on D2-40 in this context. Molecular work on the protein (podoplanin) the antibody is directed at has shown it is present in DFSP.

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SKIN LESION, LEFT SHOULDER, EXCISION:
- DERMATOFIBROMA.

Ezcema

General

• A nebulous thingy.
• Very common.

DDx:

• Contact allergy.
• Drug reaction.
• Food allergy.

Microscopic

Features:

• Spongiosis (epidermal edema); keratinocytes spacing increased - key feature.
• +/-Interdermal vesicles.
• +/-Eosinophils (may suggest Rx reaction).
• Perivascular lymphocytes.

Acne vulgaris

General

• Extremely common - esp. among adolescents.
• Very rarely seen by pathologists.

Treatments:

• Antibiotic (minocycline).
• Isotretinoin AKA all-trans retinoic acid (ATRA).

Gross

• Papules, pustules, nodules or cysts.
  • White, black or erythematous.

Images:

• Blackheads (WC).

Microscopic

Features:

• Folliculitis:
  • Neutrophils around hair follicle and infiltrate into it - including the follicular canal.
• Epidermal invagination or cyst at site of a hair follicle - contains:
  • Sebum.
  • +/-Bacteria (Propionibacterium acnes) and inflammatory cells - typically neurophils.

Subtyped into:

1. Open comedones ("blackheads") - no extension to epidermal surface.
2. Closed comedones ("whiteheads") - to epidermal surface have wide opening.

DDx - acneiform disorder:

• Rosacea.
• Infective folliculitis.
• Perioral dermatitis.
• Acne vulgaris.

Image:

• Acne (dermnet.com).

Solar elastosis

• AKA actinic elastosis.

General

• Very common.
• Caused by sun exposure - specifically UV light.
  • Severity correlated with cumulative exposure to UV light..
• Often co-localized with skin cancers - as UV light is risk factor for skin cancers.
• Benign.

Microscopic

Features:

• Grey, spaghetti-like material in the superficial dermis.

DDx:

• Actinic keratosis.
• Basal cell carcinoma.
• Squamous cell carcinoma.

Note:

• It doesn't really look like anything else.
  • The DDx above is things to think about that are associated with sun damaged skin.

Images:

• WC:
  • Solar elastosis - intermed. mag. (WC).
  • Solar elastosis - high mag. (WC).
• www:
  • Solar elastosis - several images (dermpathexpert.com).

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SKIN, RIGHT CHEEK, RE-EXCISION:
- DERMAL SCAR.
- EXTENSIVE SOLAR ELASTOSIS.

Prominent blood vessels

SKIN LESION, LEFT CHEEK, BIOPSY:
- SKIN WITH SOLAR ELASTOSIS AND PROMINENT SMALL BLOOD VESSELS.

Micro

The sections show hair bearing skin with solar elastosis and numerous small dilated blood vessels. The dermis is mildly fibrotic. Compact keratin is present.

The epidermis matures to the surface. A granular layer is present. There is no basal epidermal atypia. No melanocytic nests are identified. There is no palisading of the basal cells. Rare scattered lymphocytes are in the dermis.

Very common - viral

Verruca vulgaris

• AKA common wart.

General

• Etiology - HPV.
• Very common.

Notes:

• Related to condyloma acuminatum.

Gross

Features:

• Papule or plaque with granular surface.
• Classic location: hand.

Images:

• Wart (WC).
• Wart - animated (WC).

Microscopic

Features:

• Hyperkeratosis (more keratin - thick stratum corneum) - in "columns"; keratin in separate towers - not a flat thick sheet.
• Hypergranulosis (thicker stratum granulosum).
• Papillomatous hyperplasia:
  • Rete ridge lengthening (~7-10x normal) and thickening.
  • Rete ridge curvature toward the centre of the lesion (like the roads to the Palace of Versailles) - important.
• Large blood vessels at the dermal-epidermal junction - between the rete ridges.
• +/-Viral changes - perinuclear halo, nucleus small and hyperchromatic - virtually diagnostic when present.
  • +/-Binucleation.

Memory device: there is more of everything - more s. corneum, s. granulosum, s. spinosum, longer rete ridges, more (larger) blood vessels.

DDx:

• Squamous cell carcinoma - nuclear atypia full thickness and often more pronounced.
• Hypertrophic actinic keratosis - often accompanied by solar elastosis.
  • Actinic keratosis with superimposed lichen simplex chronicus.
• Seborrheic keratosis - may have focal clear cell changes.
• Condyloma accuminatum - genital region.

Images:

• WC:
  • Verruca vulgaris - very low mag. (WC).
  • Verruca vulgaris - intermed mag. (WC).
• www:
  • Verruca vulgaris (unibas.ch).

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SKIN LESION, RIGHT LOWER LEG, SHAVE BIOPSY:
- VERRUCA VULGARIS.

Micro

The sections show skin with elongated rete ridges, acanthosis, hypergranulosis, hyperkeratosis in vertical columns, focal parakeratosis, dilated blood vessels at the dermal-epidermal junction and koilocytic change. Mild basilar nuclear atypia is present.

Without koilocytes

The sections show skin with elongated rete ridges that curve toward the centre of the lesion, acanthosis, hypergranulosis, hyperkeratosis in vertical columns, and dilated blood vessels at the dermal-epidermal junction. Minimal basilar nuclear enlargement is present. No definite koilocytic change is apparent.

No parakeratosis is identified. Mild solar elastosis is identified. No melanocytic nests are apparent. Mitotic activity is not apparent.

Verruca plana

General

• Common.
• Usu. hands and face.

Microscopic

Features:

• Orthokeratosis with basketweave pattern.
• Hypergranulosis.
• Viral keratohyaline.
• Koilocytes.
• Acanthosis - yet flat surface and base.

Notes:

• It differs from verruca vulgaris... (1) orthokeratosis, (2) flat surface and base.

Less common

Chronic folliculitis

Folliculitis redirect here.

General

• Common.
• Infrequently biopsied.

Gross

• Erythema.

DDx gross:

• Melanocytic lesions.

Microscopic

Features:

• Inflammation around the hair follicle - key feature.
  • Lymphocytes - usu. predominant.
• +/-Chronic changes:
  • Acanthosis.
  • Hyperkeratosis.
  • Hypergranulosis.

DDx:

• Acne vulgaris.

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SKIN LESION, UPPER ARM, BIOPSY:
- CHRONIC FOLLICULITIS WITH SECONDARY SURFACE CHANGES.

Micro

The sections show hair-bearing skin with abundant lymphocytes around and within the hair follicle wall.

The non-hair follicle epidermis has acanthosis, hypergranulosis and compact hyperkeratosis. There is no inflammatory cell infiltrate in the non-hair follicle epidermis or at the non-hair follicle interface.

There are no granulomas.

Clear cell acanthoma

General

• Benign.
• Elderly.
• Classically on the leg.
• Rare.
• Clinically not distinct.
  • Suspected clinically in only ~3% of cases.

Microscopic

Features:

• Psoriasiform pattern - epidermal thickening (acanthosis).
• Keratinocytes:
  • Pale or light pink cytoplasm (when compared to surrounding non-lesional keratinocytes).
  • Separated from one another (spongiosis).
• +/-Stratum corneum neutrophils.

DDx:

• Psoriasis vulgaris.

Images:

• CCA (drmihm.com).
• CCA - low mag. (dermatlas.com).
• CCA - high mag. (dermatlas.com).

Chondrodermatitis nodularis chronica helicis

• AKA chondrodermatitis nodularis helicis.
• Abbreviated CNCH.

General

• Tender/painful - key clinical feature.
• Typically right ear - people more often sleep on this one.
• Usually >40 years old.

Etiology:

• Trauma/mechanical.

Gross

• Papule on ear.
• +/-Erythematous.
• +/-Crust.

Clinical DDx:

• BCC.
• SCC.

Images:

• CNCH (WC).
• CNCH (dermnetnz.org).

Microscopic

Features:

• Dermal inflammation.
• Epithelial hyperlasia.
• Fibrosis.
• Cartilaginous pathology:
  • Perichondrial inflammation - key feature.
  • Perichondrial disruption.
  • +/-Necrosis.
  • +/-Hemorrhage.

Images:

• CNCH (dermpedia.org).
• CNCH (surgicalpathologyatlas.com).
• CNCH (dermatlas.med.jhmi.edu).

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Superficial biopsy

SKIN LESION, LEFT ANTIHELIX OF EAR, BIOPSY:
- SUPERFICIAL SKIN WITH ACANTHOSIS, HYPERKERATOSIS, MODERATE SOLAR ELASTOSIS, 
  HYPERGRANULOSIS AND A MILD LYMPHOCYTIC PERIVASCULAR INFILTRATE.
- NO CARTILAGE IS IDENTIFIED.
- NEGATIVE FOR DYSPLASIA AND MALIGNANCY.

COMMENT:
The findings are non-specific. Chondrodermatitis cannot be excluded.

Cutaneous calcinosis

• AKA calcinosis cutis.

General

• Benign in itself; underlying cause may not be benign.
• May be a scrotal lesion - known as scrotal calcinosis.

Subtypes:

1. Dystrophic - due to death of cells; may be related to a tumour.
2. Metastatic - due to chronic renal failure; hyperkalemia; paraneoplastic phenomenon.
3. Iatrogenic - post surgical.
4. Idiopathic.

Microscopic

Features:

• Dermal calcification:
  • Acellular purple blobs on H&E.
    • +/-Artefactual tearing of surrounding tissue due to processing (cutting).
    • +/-Small artefactual lines ~1-2 micrometers due to processing (cutting).
  • Usu. well-circumscribed.

Images:

• Calcinosis cutis (blogspot.com).

Dilated pore of Winer

General

• Benign.
• Looks like zit.

Microscopic

Features:

• Dilated hair follicle with keratin.
• Acanthosis.
• Budding of epidermis (into dermis).

Lichenoid keratosis

• AKA lichen planus-like keratosis.
• AKA lichenoid keratosis.

General

• Caucasians - middle age or older.
• May be a variant of seborrheic keratosis (with marked inflammation).

Clinical DDx:

• Basal cell carcinoma, squamous cell carcinoma of the skin, melanocytic neoplasm.

Microscopic

Features:

• Hyperkeratosis.
• Parakeratosis.
• Band of inflammatory cells at DE junction (lichenoid inflammation).
• Dead keratinocytes (Civatte bodies).
• Dermal melanophages.

DDx:

• Lichen planus - need clinical correlation (mucosal lesions).
• Drug reaction.
• Cutaneous T-cell lymphoma.
• Regressed melanocytic lesion, esp. malignant melanoma.
• Lichenoid actinic keratosis - has atypical hyperchromatic basal cells - esp. at edge of lesion, usu. in the context of solar elastosis.

Images:

• Lichenoid keratosis (dermpathexpert.com).

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SKIN LESION, MID-MIDDLE BACK, PUNCH BIOPSY:
- LICHENOID KERATOSIS.

Granuloma annulare

General

• Benign and self-limited condition.
• Etiology unknown - may be assoc. with trauma.

Gross

• Typically extremities - usu. arms and hands.

Microscopic

Features:

• Dermal palisading granuloma - typically superficial-to-mid dermis - surrounds:
  • Necrotic collagen - key feature.
    • Nuclei "missing" - have undergone karyolysis.
  • Mucin - important.
    • Loose/pale, paucicellular, eosinophilic.
• Chronic inflammatory cells.

Notes:

1. There may be multiple small foci with intervening normal dermis.
2. Granuloma annulare can be subclassified into subcutaneous and interstitial.
3. Histomorphologically similar to Rheumatoid nodule.
4. Neutrophils may be seen.

DDx:

• Necrobiosis lipoidica - little mucin, no normal dermis between foci, plasma cells - common, may involve the fat - tend to be deeper.
• Rheumatoid nodule - has fibrin in the core of the granuloma (instead of mucin), multinucleated macrophages more common.
• Epithelioid sarcoma - esp. if the lesion appears to be mid-to-deep dermis.

Images:

• WC:
  • Granuloma annulare - intermed. mag. (WC).
  • Granuloma annulare - high mag. (WC).
  • Granuloma annular - palisaded granuloma - high mag. (WC).
• www:
  • Granuloma annulare (dermaamin.com).

Stains

• Alcian blue (pH 2.5) +ve (for mucin).

Image:

• Granuloma annulare (nih.gov).

Necrobiosis lipoidica

General

Associated with:

• Diabetes mellitus - known as necrobiosis lipoidica diabeticorum.
• Rheumatoid arthritis.

Microscopic

Features:

• Dermal palisading granuloma around:
  • Necrotic collagen - key feature.
    • Nuclei "missing" - have undergone karyolysis.
• Little mucin, no normal dermis between foci.
• Plasma cells - common.
• May involve adipose tissue.

DDx:

• Granuloma annulare - more mucin, normal dermis between foci, plasma cells uncommon, no fat involvement - usu. more superficial.
• Rheumatoid nodule.

Images:

• Necrobiosis lipoidica (dermatology.cdlib.org).
• Necrobiosis lipoidica (drmihm.com).
• Necrobiosis lipoidica (dermnetnz.org).

Keloid

• Hypertrophic scar redirects to this section.

General

• Sites of previous trauma/surgery, esp. in dark skinned individuals.

Microscopic

Features:

• Thick collagen bundles - surrounded by paler staining fibroblasts - key feature.
• Lesion replaces adnexal structures, e.g. hair, sweat glands.

DDx:

• Hypertrophic scar.

NB:

• Reported as "keloidal-type collagen"; the clinician decides between hypertrophic scar and keloid.

Images:

• WC:
  • Keloid - low mag. (WC).
  • Keloid - intermed. mag. (WC).
  • Keloid - high mag. (WC).
• www:
  • Keloid (ucsf.edu).

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SKIN LESION, LEFT SCAPULA, EXCISION:
- DERMAL SCAR WITH KELOIDAL-TYPE COLLAGEN, SEE COMMENT.

COMMENT:
The findings are consistent with a hypetrophic scar and keloid; clinical correlation is required.

Angiofibroma

See also: nasopharyngeal angiofibroma.

Should not be confused with angiokeratoma.

General

• May be seen in the context of tuberous sclerosis - especially "butterfly area of the face".
• Solitary lesions in adults are known as fibrous papules and classically arise on the nose.

Clinical:

• Firm, dome-shaped, flesh coloured.

Microscopic

Features:

• Dome-shaped.
• Fibrotic dermis.
  • Enlarged fibroblasts.
• Dilated small vessels.

DDx:

• Benign fibrous papule - solitary, nose lesion.

Image:

• Angiofibroma (drdittmar.lu).

Benign fibrous papule

• AKA fibrous papule.

General

• An angiofibroma on the face that is solitary.

Gross

• Solitary lesion of the face - important.
  • Usually on the nose.

Microscopic

Features:

• Dome-shaped.
• Fibrotic dermis.
  • Enlarged fibroblasts.
• Dilated small vessels.
• +/-Multinucleated stromal cells.
• +/-Stellate cells.

DDx:

• Angiofibroma - not solitary or not on the nose.

Note:

• Several variants exist.

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SKIN LESION, CHIN, BIOPSY:
- BENIGN FIBROUS PAPULE.

Molluscum contagiosum

• Abbreviated MC.

General

• Etiology: caused by molluscum contagiosum virus.
• May be abundant in immune deficient individuals, e.g. HIV/AIDS.

Gross

Features:

• Dome-shaped papules, flesh coloured or pearly.
• Usually face or trunk.
• +/-Central umbilication.
  • Central depression.

DDx - gross:

• Skin tag.

Image:

• Molluscum contagiosum (WC).

Microscopic

Features:

• A suprabasilar epidermal lesion consisting of "molluscum bodies" -- in other words "molluscum bodies" are found above the stratum basale +/- extension to the skin surface.
  • Molluscum bodies - key feature:
    • Large cells with (granular) eosinophilic cytoplasmic inclusions.
      • The inclusions usually fill the cytoplasm.
      • Inclusions are usually one per cell... but may be multiple.
    • Small peripheral nucleus.
• +/-Lymphocytes.

Notes:

• Molluscum bodies very vaguely resemble signet ring cells -- but:
  • Cytoplasm is eosinophilic and granular.
  • Nucleus usually smaller than in signet ring cells.
  • Molluscum bodies are only in the epidermis - an uncommon place to find SRCs without finding them elsewhere.
• The granular eosinophilic cytoplasmic inclusions represents accumulated virons.
• Molluscum bodies "grow" toward the surface

DDx:

• Nothing really - it is very distinctive.

Images:

• Molluscum contagiosum - high mag. (WC).
• Molluscum contagiosum - low magnification (WC).
• Molluscum contagiosum (WC).

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SKIN LESION ("SKIN TAG"), EXCISION:
- MOLLUSCUM CONTAGIOSUM.

Micro

The section shows fragments of skin with epithelium on three sides. Large suprabasilar cells with eosinophilic intracytoplasmic inclusions (molluscum bodies) and small eccentric nuclei are present, and extend to the skin surface. The epithelium is acanthotic; however, it matures to the surface. There is no significant inflammation.

Superficial dermal infiltrates

Discussed in detail by Alsaad and Ghazarian.

Dermal perivascular lymphoeosinophilic infiltration

• Abbreviated DPLI.

Microscopic appearance is just what it is called:

• Lymphocytes and eosinophils around the vessels in the superficial dermis.

DDx:

• Insect bite - classically wedge-shaped.
• Drug reaction.
• Urticarial reaction.
• Prevesicular early stage of bullous pemphigoid.
• HIV related dermatoses.

Notes:

• May superficially resemble cutaneous lymphoma.

Images:

• DPLI - very low mag. (WC).
• DPLI - very high mag. (WC).

Congenital dermal melanocytosis

• AKA Mongolian spots.
• Classically seen in asian children.

Gross:

• Brown or blue-grey patch in the lumbosacral area.

Mastocytosis

General

• Abundance of mast cells.

Classification:

1. Cutaneous (only) - usually children.
   • Urticaria pigmentosa.
   • Others.
2. Systemic - usually adults.
   • Indolent subvariant.
   • Aggressive subvariant.
   • Leukemic subvariant.

Microscopic

Features:

• Cells in the superficial/mid dermis that are:
  • Lymphocyte-like with more cytoplasm that is granular.
    • Cells may have spindled or stellate morphology.
    • Tend to be more abundant around vessels.
• +/-Eosinophils (common).
• +/-Edema - often prominent; gives cells a white halo.

Notes:

• Lymphocyte vs. mast cell:
  • Lymphocytes = round; mast cells = ovoid.

Images:

• www:
  • Mastocytosis - low res. (jameswpattersonmd.com).
  • Mastocytosis - bone marrow - several images (upmc.edu).
• WC:
  • Mastocytosis - high mag. (WC).
  • Mastocytosis - very high mag. (WC).
  • Systemic mastocytosis - several images (upmc.edu).

Stains

• Toluidine blue -- highlights the granules.

IHC

• CD117 +ve.
• Tryptase +ve.

Ichthyosis

General

• Comes in different flavours.
• Usu. inherited... thus a pediatric condition.

Gross

• Fish scale-like appearance.

Image:

• Ichtyosis (WC).

Microscopic

Features:

• Thick stratum corneum without basket-weave pattern.

Palmar fibromatosis

Main article: Fibromatosis

• AKA Dupuytren's contracture.
• AKA Dupuytren disease.

General

Clinical:

• Usually older - 60s or 70s (years old).
• Male > female.
• Associated with:
  • Alcohol abuse.
• May be familial.

Gross

• Ring finger - classic location.^{[citation needed]}
• Nodular.
• Poorly demarcated.

Image:

• Palmar fibromatosis (WC).

Microscopic

Features:

• Poorly demarcated, usu. multiple lesions/multiple nodules.
• Composed of bland spindle cells in dense collagen.
  • Pale grey cytoplasm (moderate quantity).
  • Pale ovoid nuclei with small round nucleoli.
• Giant cells - rare.

Note:

• No nuclear atypia.
• Mitotic figures - rarely present, none atypical.
• May see Pacinian corpuscle (AKA lamellar corpuscle) as an incidental finding.

DDx:

• Calcifying aponeurotic fibroma - calcification, chondroid differentiation, usu. < 20 years old.
• Extra-abdominal desmoid fibromatosis - extremely rare on hands and feet, muscle infiltrative.
• Inclusion body fibromatosis.
• Fibrosarcoma - atypia, necrosis, herring-bone pattern.
• Synovial sarcoma - one mass.
• Epithelioid sarcoma - necrosis, atypia.
• Metastatic metaplastic carcinoma, e.g. metaplastic breast carcinoma - extremely uncommon.

Images:

• Palmer fibromatosis (biomedsearch.com).
• Palmar fibromatosis (unibas.ch).
• Pacinian corpuscle (WC).
• Tendon without fibromatosis - intermed. mag. (WC).

IHC

• Beta-catenin +ve (cytoplasmic & nuclear).

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PALMAR FASCIA, LEFT, FASCIECTOMY:
- PALMAR FIBROMATOSIS.

Micro

The sections show multiple poorly-demarcated nodules composed of bland spindle cells with moderate pale grey cytoplasm and pale ellipsoid nuclei with small round nucleoli. The poorly-demarcated nodules are completely surrounded by dense collagen. Calcification is not present. There is no nuclear atypia or necrosis. Mitotic activity is not identified. Benign fibroadipose tissue is present.

Missed fibromatosis

PALMAR FASCIA, LEFT, FASCIECTOMY:
- PALMAR FASCIA WITHIN NORMAL LIMITS AND BENIGN FIBROADIPOSE TISSUE -- IN AN
  INDIVIDUAL WITH A CLINICAL HISTORY OF PALMAR FIBROMATOSIS.
- NEGATIVE FOR MALIGNANCY.

Micro

The sections show dense collagen (tendon) without an apparent pathology. Calcification is not present. There is no nuclear atypia or necrosis. Mitotic activity is not identified. Benign fibroadipose tissue is present. Lamellar corpuscles are present. The tissue was submitted in toto and levels were cut.

Straight

PALMAR FASCIA, RIGHT, FASCIECTOMY:
- PALMAR FASCIA WITHIN NORMAL LIMITS.
- NEGATIVE FOR FIBROMATOSIS.

COMMENT:
The tissue was submitted in toto and levels were cut.

Micro

The sections show dense collagen (tendon) without an apparent pathology. Calcification is not present. There is no nuclear atypia or necrosis. Mitotic activity is not identified. Benign fibroadipose tissue is present. Lamellar corpuscles are present.

Angiomyoma

• Do not confuse with angiomyxoma.

General

• Benign.
• Female > male.

Microscopic

Features:

• Well-circumscribed lesion with fascicular architecture.
• Spindle cells/epithelioid cell with moderate eosinophilic (pink) cytoplasm.
• Thick-walled blood vessels. (???)

Images:

• Angiomymoma (WC).
• Angiomymoma (WC).

Angiokeratoma

General

• Rare.
• May be seen in the context of Fabry disease.

Notes:

• Shouldn't be confused with angiofibroma which is associated tuberous sclerosis.

Microscopic

Features:

• Ectatic superficial dermal vessels.
• Overlying hyperkeratosis (thick stratum corneum).

Others features:^{[citation needed]}

• Irregular acanthosis.
• Longer rete ridges.

DDx:

• Venous lake.

Images:

• WC:
  • Angiokeratoma - low mag. (WC).
  • Angiokeratoma - intermed. mag. (WC).
• www:
  • Angiokeratoma (pathologyoutlines.com).

Inverted follicular keratosis

• Abbreviated IFK.

General

• Benign skin lesion.
• Central face - middle age.
• Uncommon.
• May be considered a variant of seborrheic keratosis that is predominantly endophytic.

Clinical DDx:

• BCC.
• Wart.

Microscopic

Features:

• Keratinocyte of cytologically benign proliferation.
• "Squamous eddies" (whorls of keratin).
• Coarse keratohyaline granules.

DDx:

• Squamous cell carcinoma of the skin.
• Trichilemmoma.
• Seborrheic keratosis - has an exophytic component.

Images:

• Inverted follicular keratosis - low mag. (flickr.com).
• Inverted follicular keratosis - high mag. (flickr.com).
• Inverted follicular keratosis - several images (mckeedermpath.com).

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SKIN LESION, FACE, BIOPSY:
- INVERTED FOLLICULAR KERATOSIS.

Focal cutaneous mucinosis

General

• Benign.
• May be associated with systemic disease.

Microscopic

Features:

• Light blue whispy material in the dermis - key feature.

DDx:

• Dermal edema.
• Digital mucous cyst.

Panniculitis

Main article: Panniculitis

This is dealt with in the panniculitis article.

DDx for panniculitis:

• Erythema nodosum.
• Erythema induratum.
• Self-inflicted trauma.
• Systemic lupus erythematosus.
• Weird stuff.

Rare

Necrotizing fasciitis

Not to be confused with nodular fasciitis.

• AKA flesh-eating disease.

General

• High mortality.
• May be diagnosed at frozen section.
• Classically associated with Group A streptococcus.

Treatment:

• Operative debridement.

Microscopic

Features:

• Necrosis of fascia - key feature.
  • PMNs and necrotic debris (amorphous grey or pink material).

Note:

• Fat lobules between septae may be normal.

DDx:

• Cellulitis.

Images:

• Necrotizing fasciitis - intermed. mag. (WC).
• Necrotizing fasciitis - high mag. (WC).

Porokeratosis

General

• Genetic.
• Several subtypes.

Notes:

• Not the same as punctate porokeratotic keratoderma.

Microscopic

Features:

• Cornoid lamella (pathognomonic) - key feature:
  • Compact keratosis over a hair follicle.
• +/-Rete ridge loss.

Images:

• WC:
  • Porokeratosis - intermed. mag. (WC).
  • Porokeratosis - very high mag. (WC).

Nevus sebaceous

• AKA nevus sebaceous of Jadassohn.

General

• Congenital - considered a hamartoma.
• Usually sporadic - may be transmitted autosomal dominant.
• Malignant tumours may arise within a nevus sebaceous.

Gross

Features:

• Head and neck plaque or papule with:
  • Well-circumscribed borders.
  • Waxy, yellow appearance.
• Area usu. devoid of hair.

DDx - gross:

• Seborrheic keratosis.

Image:

• NS (dermnet.com).

Microscopic

Features:

• Abundant sebaceous glands.
• Immature/abortive hair follicles.
  • No normal terminal hair follicles.
• Papillomatous epidermal hyperplasia.

Images:

• NS (WC).
• NS (dermnet.com).

Nevus lipomatosus superficialis

• Abbreviated NLS.
• AKA nevus lipomatosus cutaneous superficialis, abbreviated NLCS.
• AKA nevus lipomatosus.

General

• Rare.
• Congenital - considered a hamartoma.
• Usually young adults.

Clinically separated into:

• Solitary - one lesion.
• Multiple - more than one lesion.

Gross

Features:

• Pedunculated lesion.
• Soft.
• Usually lower trunk or gluteal region.

Image:

• NLS (nih.gov).

Microscopic

Features:

• Benign adipose tissue in the dermis.
  • Adipocytes in reticular dermis +/- papillary dermis.

DDx:

• Lipoma.
• Fibroepithelial polyp (skin tag).

Images:

• NLS (dermamin.com).
• NLS (humpath.com).
• NLS (nih.gov).
• Nevus lipomatosus (dermpedia.org).

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SKIN LESION ("SKIN TAG"), LEFT HIP, EXCISION:
- NEVUS LIPOMATOSUS SUPERFICIALIS.

Bullous disease

Main article: Bullous disease

Cysts

Main article: Dermal cysts

See also

• Dermatopathology introduction.
• Malignant skin disease.