Primary Epithelioid Sarcoma of the Conchal Bowl in a 64-Year-Old Male: A Case Report and Review of the Literature.

Epithelioid sarcoma (ES) is a distinctive malignant mesenchymal neoplasm with atypical epithelioid cells palisading around a central zone of necrosis. ES is a rare entity even in soft tissue pathology. Immunohistochemically, tumors usually show diffuse epithelial membrane antigen and cytokeratin expression and loss of nuclear INI1 (SMARCB1) expression. Here, we report a case of a 64-year-old man with ES arising in the left conchal bowl. Given the clinical presentation including patient's age, sun-exposed area of skin, and slow-growing, asymptomatic, small pink pearly papule, this patient was initially misdiagnosed with basal cell carcinoma clinically and treated with topical imiquimod at an outside facility. The lesion continued to grow and eventually became symptomatic despite the treatment after which biopsy was obtained. Despite the unusual anatomic site and the patient's age, the microscopic and immunohistochemical findings were characteristic of conventional-type ES. Our case shows that ES can arise in rare locations and in older adults where it may be more easily misdiagnosed clinically and pathologically as a nonmelanoma skin cancer.