Dermal cysts
Dermal cysts happen and are common. Dermatopathologists can diagnose 'em.
Cysts
Common types:[1]
- Epidermal cyst (sebaceous cyst) -- most common.
- Pilar (tricheilemmal) cyst.
- Dermoid cyst.
- Ganglion cyst.
- Milicem.
EM, SJS, TEN
- SJS and TEN are on a spectrum, EM is considered separate.
Erythema multiforme (EM)
Stevens-Johnson Syndrome (SJS) and Toxic Epidermal Necrolysis (TEN)
Rx causes of SJS:
- NSAIDs,
- anticonvulsants,
- sulfonamides,
- penicillins.
TEN more severe form SJS.
Definition:
- >30% sheet-like epidermal detachment, diffuse erythema, severe mucous membrane involvement
- most TEN (80%) Rx-related, only 50% of SJS Rx-related
Venous lake
- Dilated vein.
Microscopic
Features:[2]
- Lined by endothelium.
- Blood in lumen.
- +/-Fibrin in lumen.
DDx:
- Angiokeratoma.
- Ectatic superficial dermal vessels.
- Irregular acanthosis.
- Longer rete ridges.
Neurofibromatosis (von Recklinghausen's disease)
Etiology
- Genetic - autosomal dominant disorder.
Management
- Follow for malignant transformation of neurofibroma --> neurofibrosarcoma.
Treatment
- Excise suspicious lesions & lesions that are painful.
Collagenous fibroma
General
- Benign.
- Used to be known as desmoblastic fibroblastoma.
Epidemiology
- May be on the lip.
- acellular stroma with abundant collagen.
- no nuclear atypia.
Dermatomyositis
Gross
- Have lesions on the knuckle - Gottron's papulle
Histology
- Lymphocytic interface dermatitis (inflammation at the dermal-epidermal junction).
- Loss of rete ridges.
Systemic lupus erythematosus
- Lymphocytic interface dermatitis.[5]
Familial benign pemphigus
- AKA Hailey-Hailey disease. Was described by two brothers - that's why it is Hailey-Hailey.[6]
Etiology
- Autosomal dominant with incomplete penetration.[6]
- Desmosomal defect - due to mutation in the gene ATP2C1.[6]
Clinical
- Chest.
- Intriginous regions (?sp).
- Typically presents individual in their 30s and 40s.[6]
Histology
- Hair folicles spared.
- Epidermis thickened.
DDx
- May resemble pemphigus vulgaris.
Epidermal inclusion cyst
- AKA epidermal cyst.
General
- Very common.
Microscopic
Feature:
- Cyst lining has a granular layer - key feature.[7]
- Trapped collagen bundles at edge of lesion with surrounded by fibroblasts.
- Keratin.
Image:
DDx:
- Dermatofibrosarcoma - if lesion is large.
- Pilar cyst - no granular layer.