Squamous cell carcinoma with osteoclast-like giant cells: a morphologically heterologous group including carcinosarcoma and squamous cell carcinoma with stromal changes.

Cutaneous squamous cell carcinoma (SCC) with osteoclast-like giant cells (hereafter, osteoclastic cells) is very rare; eight cases have been reported since 2006. Whether the osteoclastic cells represents a reactive or neoplastic change remains a matter of debate. Osteoclastic cells are often observed in the sarcomatous component of cutaneous carcinosarcoma. SCC with osteoclastic cells is a heterogeneous condition that includes SCC with stromal changes containing osteoclastic cells (also known as osteoclast-like giant cell reaction) and carcinosarcoma. In some cases, SCC with an associated osteoclast-like giant cell reaction has been differentiated from carcinosarcoma based on the degree of cytologic atypia in non-epithelial components. We summarized the clinical and histopathologic characteristics of 11 patients of SCC with osteoclastic cells, including our two cases of SCC with an osteoclast-like giant cell reaction and one case of carcinosarcoma. The affected patients were old and more likely to be male (64%). Seven cases (64%) were in the head and neck. Moreover, multiple features of high risk SCC were observed, such as a tumor size greater than 2 cm (56%), moderate or poor differentiation (100%), recurrence (33%) and nodal metastasis (17%) after excision and immunosuppression (27%). Interestingly, half of the previously reported cases of SCC with osteoclastic giant cell reaction had histopathologic findings that were overlapping with those of carcinosarcoma.