DESMOPLASTIC TRICHILEMMOMA - A CASE-REPORT WITH IMMUNOHISTOCHEMICAL CHARACTERIZATION OF THE EXTRACELLULAR-MATRIX COMPONENTS

The case of an unusual desmoplastic variant of trichilemmoma arising i n the neck of a 56-year-old man is reported. The tumour was characteri zed by the presence of a densely sclerotic stroma, surrounded by lobul es of epithelial cells with features of outer root sheath differentiat ion, including glycogen-rich, clear cytoplasm and peripheral palisadin g, In the central part of the tumour, irregular cords of epithelial ce lls entrapped in the desmoplastic stroma were found. Differential diag nosis of this rare tumour includes invasive squamous cell carcinoma, m orphea-like type basal cell carcinoma, desmoplastic trichoepithelioma and desmoplastic trichoblastoma. By immunohistochemistry, the tumour e pithelium stained with anti-cytokeratin antibodies while the stromal c ells were positive with vimentin, The centro-tumoral extracellular mat rix shelved a diffuse and intense positivity for type I collagen and t enascin, whereas stains for laminin and type IV collagen were uniforml y negative, We suggest that tenascin could be secreted by the epitheli al neoplastic cells and play a role in the mesenchymal response, which results in desmoplasia.