Granular cell basal cell carcinoma.

Granular cell basal cell carcinoma (BCC) is a rare histologic variant of BCC. In this, the third reported case, the tumor consisted almost entirely of granular cells. By electron microscopy, these cells were filled with pleomorphic lysosome-like granules lined by unit membranes and containing homogeneous or granular electron-dense bodies, membranous debris and amorphous material. The epithelial origin of the tumor was suggested by the characteristic light microscopic appearance of tumor cell islands with some areas of peripheral palisading, and was confirmed by electron microscopic features of numerous well-formed pentalaminate desmosome junctions and sparse cytoplasmic tonofilament bundles, some of which showed attachments to the desmosomes. Histochemical immunoperoxidase stains for lysozyme showed no cytoplasmic lysozyme activity, in common with other granular cell tumors, but ultrastructural examination did not reveal angulate bodies, in contrast to findings in non-epithelial granular cell tumors.