## Histopathology of Lichen Planus **Key Point:** The classic histological triad of lichen planus consists of: 1. **Hyperkeratosis** (sometimes with hypergranulosis) 2. **Saw-tooth pattern of acanthosis** (also called "wedge-shaped" or "jagged" acanthosis) 3. **Dense lichenoid (band-like) lymphocytic infiltrate** in the superficial dermis that obscures the dermoepidermal junction ### Additional Characteristic Features - **Civatte bodies** (colloid bodies): Apoptotic keratinocytes at the basal layer, visible as eosinophilic globules - **Basal layer vacuolization**: Degeneration of basal keratinocytes - **Absence of spongiosis**: Unlike eczema, lichen planus does NOT show intercellular edema - **Lymphocytic infiltrate composition**: Predominantly CD8+ T cells (cytotoxic) and CD4+ T cells **High-Yield:** The saw-tooth acanthosis pattern is pathognomonic and distinguishes lichen planus from other lichenoid dermatoses (e.g., lichenoid drug reaction, lichen nitidus). **Clinical Pearl:** Civatte bodies are not specific to lichen planus but are highly characteristic when seen in the correct clinical context. ### Differential Histology | Feature | Lichen Planus | Psoriasis | Eczema | |---------|---------------|-----------|--------| | Acanthosis pattern | Saw-tooth (jagged) | Regular, uniform | Variable | | Infiltrate | Lichenoid (band-like) | Perivascular | Sparse, perivascular | | Spongiosis | Absent | Absent | Present | | Parakeratosis | Absent/minimal | Present | May be present | | Civatte bodies | Present | Absent | Absent | [cite:Robbins 10e Ch 25] 
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