The histopathology slide of a skin biopsy shown above demonstrates features characteristic of which dermatological condition?

Explanation

## Image Findings * **Hyperkeratosis** (thickening of the stratum corneum). * **Irregular acanthosis** with characteristic **'saw-tooth' rete ridges** (pointed, irregular epidermal projections into the dermis). * **Vacuolar degeneration** of the **basal cell layer** (damage and spaces within the basal keratinocytes). * Dense, **band-like lymphocytic infiltrate** at the **dermo-epidermal junction** (a continuous layer of lymphocytes obscuring the interface). * **Eosinophilic Civatte bodies** (apoptotic keratinocytes) present in the basal layer and upper dermis. ## Diagnosis **Key Point:** The presence of a dense, band-like lymphocytic infiltrate at the dermo-epidermal junction with saw-tooth rete ridges and basal cell vacuolar degeneration is pathognomonic for **Lichen Planus**. The image clearly demonstrates the classic histopathological triad of **Lichen Planus**: **hyperkeratosis**, **irregular acanthosis** with distinctive **'saw-tooth' rete ridges**, and a dense, **band-like lymphocytic infiltrate** at the dermo-epidermal junction. This inflammatory infiltrate causes damage to the basal keratinocytes, leading to **vacuolar degeneration** and the formation of **Civatte bodies** (apoptotic keratinocytes), which are seen as eosinophilic globules. These findings collectively represent a **lichenoid tissue reaction**, which is the hallmark of Lichen Planus. ## Differential Diagnosis | Feature | Correct Dx: Lichen Planus | Alt 1: Psoriasis | Alt 2: Eczematous Dermatitis (Acute) | | :------------------------ | :------------------------------------------------------ | :---------------------------------------------------------- | :---------------------------------------------------------- | | **Epidermis** | Irregular acanthosis, saw-tooth rete ridges | Regular acanthosis, elongated rete ridges | Spongiosis (intercellular edema), exocytosis of lymphocytes | | **Stratum Corneum** | Hyperkeratosis | Parakeratosis (nuclei retained), hyperkeratosis | Mild hyperkeratosis, serous crusts | | **Basal Layer** | Vacuolar degeneration, Civatte bodies | Intact, no significant degeneration | Intact, no significant degeneration | | **Dermo-Epidermal Junction** | Dense, band-like lymphocytic infiltrate (lichenoid) | Minimal inflammation, dilated capillaries in dermal papillae | Mild perivascular lymphocytic infiltrate | | **Specific Findings** | Civatte bodies, saw-tooth rete ridges, band-like infiltrate | Munro microabscesses, Kogoj spongiform pustules | Vesiculation (intraepidermal), crusting | ## Clinical Relevance **Clinical Pearl:** Lichen Planus commonly presents with **"6 Ps"**: Pruritic, Purple, Polygonal, Planar, Papules, and Plaques. It can affect skin, mucous membranes (Wickham's striae), nails, and hair. ## High-Yield for NEET PG **High-Yield:** The **band-like lymphocytic infiltrate** at the dermo-epidermal junction and **saw-tooth rete ridges** are the most characteristic histopathological features of Lichen Planus. **Key Point:** **Civatte bodies** are apoptotic basal keratinocytes, often seen in the basal layer or upper dermis in Lichen Planus. ## Common Traps **Warning:** Do not confuse the regular acanthosis and elongated rete ridges of **Psoriasis** with the irregular, saw-tooth rete ridges of **Lichen Planus**. Also, the presence of spongiosis is a key differentiator for eczematous dermatitis. ## Reference [cite:Robbins Basic Pathology, 10th Edition, Chapter 25: Skin, p. 1098-1099.]