Perianal Cutaneous Spindle Cell Squamous Cell Carcinoma With Myxoid Stroma: Case Report and Literature Review.

Spindle cell squamous cell carcinoma with myxoid stroma is a rare variant of squamous cell carcinoma with sarcomatoid morphology. We report a case of a 75-year-old woman with an ulcerated polypoid cutaneous mass in the perianal area. The patient had a history of clear cell renal cell carcinoma. Microscopy revealed an invasive myxoid spindle cell carcinoma without the classic squamous cell carcinoma component. The immunohistochemical study demonstrated diffuse positive reactions for p63, AE1/3, and CK5/6. The tumor cells were negative for desmin, smooth muscle actin, S100, and CD34. Fluorescent in situ hybridization was negative for EWSR1 gene rearrangement. Follow-up was remarkable for recurrence of tumor in 2 months after complete resection with negative surgical margin. This is the first case report of perianal spindle cell squamous cell carcinoma with myxoid stroma with a literature review of previous case reports from different locations.