Granular Cell Tumour — MFDS Part 1 MCQ

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HardOral PathologyGranular Cell TumourMFDS Part 1

A 42-year-old patient has a firm, painless nodule on the dorsal tongue. Biopsy shows a non-encapsulated proliferation of polygonal cells with abundant eosinophilic granular cytoplasm beneath epithelium exhibiting pseudoepitheliomatous hyperplasia. Which immunohistochemical marker would be expected to show strong, diffuse staining in the tumour cells?

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Correct answer: E — S-100 protein

The correct answer is E, S-100 protein. A painless dorsal-tongue nodule composed of polygonal cells with abundant granular eosinophilic cytoplasm and associated pseudoepitheliomatous hyperplasia is characteristic of a conventional granular cell tumour. These tumours typically show strong, diffuse S-100 immunoreactivity, supporting Schwannian differentiation. The epithelial hyperplasia can mimic squamous cell carcinoma, but cytokeratin stains the epithelial component rather than the underlying granular tumour cells. Desmin and alpha-smooth muscle actin are markers of muscle differentiation and are not characteristic of conventional granular cell tumour. CD34 is primarily associated with vascular and selected fibroblastic tumours and is not the expected diagnostic marker here.

Reference: Vered M, Carpenter WM, Buchner A. Granular cell tumor of the oral cavity: updated immunohistochemical profile. Journal of Oral Pathology & Medicine. 2009;38(1):150-159. https://pubmed.ncbi.nlm.nih.gov/19192059/