In two cases of basal cell carcinoma with prominent granular cell features, light microscopic examination showed a tumor with the general configuration of a nodular basal cell carcinoma. Focally, there were masses of cells with eosinophilic, granular cytoplasm and large cytoplasmic inclusions, strongly suggestive of granular cell myoblastoma. Ultrastructural observations in one case showed numerous lysosome-like organelles that were similar to those described for granular cell myoblastoma, but were identical to those described for the granular cell variant of ameloblastoma, a tumor that frequently resembles basal cell carcinoma. Additional features included tonofilaments and desmosomes, both of which support an epithelial origin for the granular cells in this rare variant of basal cell carcinoma.
(Arch Dermatol 115:1064-1067, 1979)