A skin biopsy from a patient with generalized pruritic, violaceous papules shows hyperkeratosis, irregular acanthosis with saw-tooth rete ridges, vacuolar degeneration of the basal layer, and a dense band-like lymphocytic infiltrate at the dermo-epidermal junction. Civatte bodies are also noted. These findings are characteristic of:

Explanation

The described histopathological features are pathognomonic for lichen planus. Key findings include: 1. **Hyperkeratosis and irregular acanthosis with saw-tooth rete ridges:** This refers to the undulating epidermal architecture. 2. **Vacuolar degeneration of the basal layer:** Damage to the basal keratinocytes. 3. **Dense band-like lymphocytic infiltrate at the dermo-epidermal junction:** This is the characteristic 'lichenoid' infiltrate. 4. **Civatte bodies:** These are apoptotic keratinocytes (colloid bodies) found in the epidermis and upper dermis. These features collectively distinguish lichen planus from psoriasis (which shows regular acanthosis, parakeratosis, Munro microabscesses), lupus erythematosus (which often has interface dermatitis but typically less dense infiltrate and prominent follicular plugging), and erythema multiforme (which shows keratinocyte necrosis and a sparse perivascular infiltrate).