Dermatopathology

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Dermatopathology is the pathology of skin.

Pathology is a significant part of dermatology and dermatologists spend five years in residency. So, it is a huge area.

Layers of the skin

  • Epidermis - outer most layer, avascular, separated from dermis by a basement membrane, epithelial tissue.
  • Dermis - below the epidermis, vascular, separated from the epidermis by a basement membrane, connective tissue.
  • Subdermis - below the dermis, connective tissue.

Layers of epidermis

Epidermis layers - from the surface to epidermal-dermal junction:

  • Stratum corneum.
  • Stratum lucidum.
    • Present only in "thick" skin.[1]
  • Stratum granulosum.
  • Stratum spinosum (aka prickle layer).
  • Stratum basale (germinativum).

Mnemonic: Corn Lovers Grow Several Bales.

Adnexal structures

The top five structures of the skin:[2]

Structure / Attribute Histomorphology Function IHC Other Image
Eccrine gland clusters of tubular structures, pale cytoplasm thermoregulation (cooling) CK7+, CEA+, CAM5.2+, EMA+ ? ?
Apocrine gland apical snouts, tubular structures ear wax, body odor ? ? ?
Sebaceous gland clusters of cells side-by-side, pale fluffy cytoplasm grease hair, sexual lubrication ? assoc. with hair follicle ?
Hair follicle linear structure keep individual warm ? assoc. with sebaceous glands ?
Nail epidermal structure ? look pretty ? ? ?

Ducts vs. glands:[3]

  • Eccrine glands - spindle-shaped myoepithelial cells surround luminal cells.
  • Eccrine ducts - cuboidal type subepithelial cells.

Common terms

  • Acanthosis = thickening of the prickle layer (stratum spinosum) of epidermis.[4]
  • Parakeratosis = retention of nuclei in the stratum corneum, normal in mucous membranes
  • Dyskeratosis = abnormal keratinization, often refers to keratinization below the stratum granulosum; keratinization above may be abnormal (dependent on body site).
  • Spongiosis = epidermal intercellular edema;[5] cells appear to have a clear halo around 'em.

Images:

Skin diseases

Cancer

Main article: Dermatologic cancer

Skin cancer is very common. The basic DDx of a malignant skin lesion is:

Non-malignant disease

Main article: Non-malignant skin disease

Non-malignant skin disease is common. It is the domain of dermatologists. It can be scary for general anatomical pathologist because the differential diagnosis is often broad, and, it's generally not something the general anatomical pathologist sees a lot of.

Bullous diseases, e.g. pemphigus vulgaris, is dealt with in the bullous disease article.

Common entities

Non-malignant non-cystic
Entity Key histologic feature Other features Clinical Stains/IHC DDx Other Image
Seborrheic keratosis (SK) horn cysts (intraepidermal collections of keratin) hyperkeratosis, brown granular material at the DE junction, sharply demarcated stuck on appearance none Fibroepithelial polyp Leser–Trélat sign = many SKs in malignancy (WC)
Dermatofibroma fibrous bundles esp. at edge of lesion "dirty fingers" = acanthosis + basal keratinocyte hyperpigmentation +/-trauma Hx CD34-, Factor VIIIa+ DFSP very common (pacificderm.org)
Fibroepithelial polyp (skin tag) on a stalk (epithelium on 3+ sides) no horn nests, no hyperkeratosis raised lesion none seborrheic keratosis very common (dermatlas.med.jhmi.edu)
Lipoma mature adipocytes - uniform size var. of size may be seen, should prompt search for lipoblasts mobile subcutaneous mass S100 (???) liposarcoma variants: angiolipoma (blood vessels), myolipoma (muscle) (ahajournals.org)
Angiofibroma fibrotic dermis, dilated capillaries enlarged (stellate fibroblasts) dome-shaped - face, boys & nosebleeds (nasopharyngeal angiofibroma) Stains/IHC DDx may be associated with tuberous sclerosis Angiofibroma (drdittmar.lu)
Keloid thick collagen bundles - surrounded by paler staining fibroblasts replaces adnexal structures site of previous trauma, esp. in blacks none dermatofibroma (???) Other ? (ucsf.edu).
Neurofibroma bland spindle cells mixed with collagen (???) may be associated with neurofibromatosis S100+ (???) dermal nevus (???) Other ? (WC)
Keratoacanthoma keratin plug, glassy pink cytoplasm, pushing downward growth minimal/no nuclear atypia grow rapidly then involute none squamous cell carcinoma some don't believe in the entity (WC)
Molluscum contagiosum suprabasilar cells with abundant granular eosinophilic cytoplasm small peripheral nucleus polypoid lesion (?) none (?) DDx (?) favourite exam case (WC)
Granuloma annulare dermal palisading granuloma around necrotic collagen mucin in centre of lesion, (peripheral) chronic inflammatory cells benign, self-limited none (CD68?) necrobiosis lipoidica, rheumatoid nodule Other ? (dermaamin.com)
Non-malignant cystic
Entity Key histologic feature Other features Clinical Stains/IHC DDx Other Image
Epidermal cyst keratin surrounded by epidermis, epidermis has granular layer cyst none pilar cyst Other? (ucsf.edu)
Pilar cyst keratin surrounded by epidermis, epidermis has no granular layer cyst none epidermal cyst Other? Image?
Pre-malignant
Entity Key histologic feature Other features Clinical Stains/IHC DDx Other Image
Actinic keratosis epidermal atypia, esp. (basal) nuclear enlargement var. of size, shape and staining yellow-brown scaly none squamous carcinoma squamous carcinoma (WC)
Common malignant
Entity Key histologic feature Other features Clinical Stains/IHC DDx Other Image
Basal cell carcinoma basaloid cells with peripheral palisading, artificial cleft Other features pearly, telangiectasia none (???) trichoepithelioma assoc. nevoid basal cell carcinoma syndrome, Bazex syndrome Image
Squamous cell carcinoma nuclear enlargement, eosinophilic cytoplasm, central nucleus small nucleolus, intercellular bridges flaky appearance p63+, HMWK+ (???) keratoacanthoma Other Image
Melanoma nuclear atypia (nucleoli), spindle and/or epithelioid morphology mitoses (esp. deep), +/-pigment, +/-nested arch., asymmetry, upward spread (into epidermis), epithelioid m. deep ABCD = Asymmetry, Borders poor demarc., Dolour dark, Diameter large S100+, Melan A+, HMB-45+, microphthalmia+, tyrosinase+ melanocytic lesions may be familial, dysplastic nevus (WC)


Less common malignant
Entity Key histologic feature Other features Clinical Stains/IHC DDx Other Image
Kaposi sarcoma vascular spindle cell lesion hyaline globules (intracytoplasmic) often HIV/AIDS HHV-8 Masson's hemangioma, angiosarcoma Other Image
Cutaneous T-cell lymphoma (mycosis fungoides) single lymphocytes in epidermis ("lymphocyte exocytosis") lymphocyte nests in the epidermis ("Pautrier microabscesses"), short arrays of lymphocytes along the basal layer of the epidermis ("epidermotropism") Clinical CD45, CD4 B cell lymphoma (?) Other (WC)

Presentations

Leukoplakia

DDx:[6]

Skin disease and systemic conditions

Acanthosis nigricans

Associated with: diabetes mellitus,[7] malignancy.[8]

Microscopic

Features BPH:[8]

  • Basal cell hyperpigmentation.
  • Prominent rete ridges.
  • Hyperkeratosis.

Images:

Others

References

  1. ↑ Busam, Klaus J. (2009). Dermatopathology: A Volume in the Foundations in Diagnostic Pathology Series (1st ed.). Saunders. pp. 1. ISBN 978-0443066542.
  2. ↑ Busam, Klaus J. (2009). Dermatopathology: A Volume in the Foundations in Diagnostic Pathology Series (1st ed.). Saunders. pp. 4-8. ISBN 978-0443066542.
  3. ↑ HJ. 27 Feb 2009.
  4. ↑ http://dictionary.reference.com/browse/acanthosis
  5. ↑ Cotran, Ramzi S.; Kumar, Vinay; Fausto, Nelson; Nelso Fausto; Robbins, Stanley L.; Abbas, Abul K. (2005). Robbins and Cotran pathologic basis of disease (7th ed.). St. Louis, Mo: Elsevier Saunders. pp. 1230. ISBN 0-7216-0187-1.
  6. ↑ Cotran, Ramzi S.; Kumar, Vinay; Fausto, Nelson; Nelso Fausto; Robbins, Stanley L.; Abbas, Abul K. (2005). Robbins and Cotran pathologic basis of disease (7th ed.). St. Louis, Mo: Elsevier Saunders. pp. 1065. ISBN 0-7216-0187-1.
  7. ↑ URL: http://www.emedicine.com/derm/topic1.htm, URL: [1].
  8. ↑ 8.0 8.1 Mitchell, Richard; Kumar, Vinay; Fausto, Nelson; Abbas, Abul K.; Aster, Jon (2011). Pocket Companion to Robbins & Cotran Pathologic Basis of Disease (8th ed.). Elsevier Saunders. pp. 596. ISBN 978-1416054542.
  9. ↑ TN07 D23.
  10. ↑ TN07 D23.
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