Epithelioid sarcoma originating in the chest wall: A case report

This report presents the sixth case of chest wall epithelioid sarcoma (ES) in a 71-year-old Japanese man. The patient was incidentally diagnosed with a soft tissue tumor between the eighth and ninth ribs, presenting with an associated bone fracture and osteolytic change. Marginal resection followed by chest wall reconstruction was performed for a definitive diagnosis. Histopathological examination revealed multinodular growth associated with collagenous stroma, mimicking a necrotizing granulomatous process. Various tumor cells were observed, including epithelioid, spindle-shaped, and rhabdoid cells. Immunohistochemical analysis, conducted on trimmed tumor samples without decalcification, revealed positivity for cytokeratin AE1/AE3, vimentin, and CD34, as well as negativity for CK7, CK20, CD31, calretinin, and D2-40. INI expression was completely absent in tumor cells. The patient was diagnosed with ES. The chest wall is an unusual location for ES, and its diagnosis requires differentiation from other epithelioid neoplasms. This case highlights the importance of trimming tumor samples before decalcification to preserve antigenicity and ensure accurate immunohistochemistry analysis.