This transcript provides a detailed histopathological analysis of a skin shave biopsy, diagnosing hypertrophic lichen planus. The speaker meticulously describes the microscopic features, including marked focal acanthosis of the epidermis, dense orthokeratosis with some parakeratosis, and prominent dilated blood vessels in the papillary dermis indicative of stasis change, a key clue for a lower leg (shin) biopsy site. A critical finding is the dense, band-like lichenoid lymphocytic infiltrate hugging the basal layer of the epidermis, particularly at the tips of the acanthotic regions. This infiltrate is shown to be actively destroying the basal layer, leading to vacuolar change and the presence of dying keratinocytes (Civatte bodies), characteristic of lichenoid interface dermatitis. The presence of eosinophils and plasma cells further distinguishes this hypertrophic variant from classic lichen planus. The discussion highlights the clinical presentation as itchy plaques and nodules on the anterior shins and notes that these lesions can sometimes mimic basal cell or squamous cell carcinomas.
Pathological Analysis of Hypertrophic Lichen Planus
0:00 Broad Shave Biopsy & Epidermal Thickening: The analysis begins with a broad shave biopsy showing focal areas of markedly thickened epidermis (acanthosis) interspersed with areas of normal thickness.
0:22 Surface Keratin & Dermal Clues: The surface exhibits thick, compact orthokeratin with some scattered parakeratosis (retained nuclei). Below, dilated blood vessels in the papillary dermis ("stasis change") are identified as a strong clue indicating the biopsy is from the lower leg, specifically the shin, a common finding in older individuals due to gravity-related blood flow.
1:36 Band-Like Infiltrate: A dense, band-like infiltrate of lymphocytes is observed at the base of the acanthotic regions, hugging the bottom of the epidermis.
1:56 Lichenoid Interface Change: Closer examination reveals a lichenoid infiltrate, where lymphocytes are actively "chewing up" and destroying the basal layer of keratinocytes and the basement membrane. This results in "vacuolar change" or "liquid vacuolar degeneration" (small bubbles) and the presence of "dying keratinocytes" (pink blobs, also called Civatte bodies). This blurred dermal-epidermal junction defines lichenoid interface dermatitis.
3:03 Diagnosis: Hypertrophic Lichen Planus: The combination of an itchy plaque on the anterior lower leg with marked, sometimes skipping, acanthosis and a band-like lichenoid interface infiltrate is diagnostic of hypertrophic lichen planus.
3:43 Distinguishing Features: Unlike regular lichen planus, hypertrophic lichen planus often features eosinophils and plasma cells within the infiltrate, as seen in this example.
4:09 Clinical Mimicry: Hypertrophic lichen planus lesions, especially solitary ones on the lower legs, can clinically resemble basal cell carcinoma or squamous cell carcinoma, often leading to biopsy for differentiation.