Granular cell basal cell carcinoma. Light microscopy, immunohistochemical and ultrastructural study.

Granular cell basal cell carcinoma (BCC) is a rare histological variant of BCC. In this, the fifth reported case, a 67-year-old male with BCC located on the nose, light microscopy examination showed a tumour with the classical configuration of nodular BCC, in which most cells had finely granular eosinophilic cytoplasm. Ultrastructural observation showed numerous lysosome-like granules filling the cytoplasm of tumour cells, along with numerous well-formed pentalaminate desmosomes. Immunohistochemical profile (including positivity for keratins C 5.2 and AE 1 and for Leu-M1), together with the presence of cytoplasmic tonofilament bundles and desmosomes, are consistent with the proposed epithelial origin of granular cells in this tumour.