An unusual infiltrative basal cell carcinoma with osteoclastic stromal changes mimicking carcinosarcoma: a case...

A 91-year-old man presented with an ulcerated nodule on his left lower eyelid. The tumor showed an epithelial component composed of basaloid and clear cells and a stroma that contained many osteoclastic giant cells. Strong, diffuse expression for cytokeratin 17 and p63 was noted in the epithelial component, whereas no staining was present in the sarcomatoid stroma, suggesting that the osteoclast-rich stromal component represented an unusual benign stromal reaction to the carcinoma rather than a manifestation of carcinosarcoma. Further supporting this interpretation was the absence of mitotic figures and low Ki-67 proliferation index (of approximately 1%) in the stromal cells. We herein reported a case of unusual infiltrative basal cell carcinoma, accompanied by a clear cell carcinomatous features and concurrent benign osteoclastic stromal changes.