Dermal cysts

Dermal cysts happen and are common. Dermatopathologists can diagnose 'em.

Cysts

Common types:

• 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.

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:

• 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.

Histo.

• 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.

Familial benign pemphigus

• AKA Hailey-Hailey disease. Was described by two brothers - that's why it is Hailey-Hailey.

Etiology

• Autosomal dominant with incomplete penetration.
• Desmosomal defect - due to mutation in the gene ATP2C1.

Clinical

• Chest.
• Intriginous regions (?sp).
• Typically presents individual in their 30s and 40s.

Histology

• Hair folicles spared.
• Epidermis thickened.

DDx

• May resemble pemphigus vulgaris.

Epidermal inclusion cyst

• Need to see keratin.

Image:

• Epidermal follicular cyst (ucsf.edu)

Micro

• Trapped collagen bundles at edge of lesion with surrounded by fibroblasts.
• Red cells.

DDx: dermatofibrosarcoma (if lesion is large)

See also

• Non-malignant skin disease
• Dermatopathology introduction