Lichen Planus

Epidemiology:

Common sites:

• extremities – wrists and elbows
• glans penis
• oral mucosa (70%)

Gross features:

• multiple
• symmetrical
• pruritic
• purple (violaceous)
• dark-brown colour in dark-skinned individuals (loss of melanin pigment into dermis)
• (flat-topped) polygonal papules or plaques
• Wickham striae – white dots or lines (zones of hypergranulosis
• resolved lesions may leave postinflammatory hyperpigmentation
• oral mucosal lesions:
• white, reticulated, or netlike areas

Histologic features:

• dense, continuous lymphocytic infiltrate along the dermoepidermal junction
• interface dermatitis
• degeneration, necrosis of basal keratinocytes
• squamatization of basal keratinocytes (resemblance in size and contour to more mature cells of the stratum spinosum
• Civatte bodies in the papillary dermis (anucleate, necrotic basal cells)
• saw-toothed, angulated, zig-zag contour of dermoepidermal junction
• acanthosis
• epidermal atrophy rarely
• hypergranulosis
• hyperkeratosis
• lichen planopilaris:
• preferentially affecting the epithelium of the hair follicles

Immunophenotype:

Marker:

Sensitivity:

Specificity:

Molecular features:

Other features:

• malignant degeneration may occur in chronic mucosal and paramucosal lesions
• self-limiting – resolves spontaneously 1-2y after onset
• oral lesions may persist
• Koebner phenomenon

References:

• Robbins 2005