Pleomorphic Dermal Sarcoma With Rare Metastasis to the Colon

A 76-year-old male presented with a firm ulcerated plaque on his right forehead. Initial superficial biopsy at an outside practice found an atypical dermal spindle proliferation suggestive of atypical fibroxanthoma (AFX). The superficial nature of the specimen limited subcutaneous evaluation. The patient was referred for Mohs micrographic surgery, and the specimen underwent pathologic evaluation. This specimen again revealed an atypical dermal spindle proliferation diffusely positive for CD10 and negative for CD34, Desmin, p63, pancytokeratin, and SOX10, now with infiltration into the subcutaneous tissue. A diagnosis of pleomorphic dermal sarcoma (PDS) was favored. Morphologically, PDS resembles AFX and shares many clinicopathologic features. It can be distinguished from AFX histologically by the presence of subcutaneous invasion, tumor necrosis, lymphovascular invasion, and/or perineural invasion. Ten months later, the patient presented with chest pain. Computed tomography scans revealed multiple lung nodules and a colon mass. Biopsy of the colonic lesion and a lung nodule indicated atypical spindle cells morphologically similar to the patient's known PDS, consistent with metastatic disease. Early recognition and treatment of PDS is critical due to its high metastatic potential. This report highlights a unique case of colonic involvement, a rare manifestation with limited documentation in current literature.