Cytokeratin-Positive Pleomorphic Chest Wall Sarcoma Mimicking MPNST: A Case Report

Undifferentiated pleomorphic sarcoma (UPS) is an uncommon high-grade soft-tissue sarcoma and remains a diagnosis of exclusion because it lacks specific differentiation and pathognomonic markers. Primary chest-wall involvement is rare, and epithelial-marker expression may complicate diagnosis by broadening the differential diagnosis.

A 62-year-old male carpenter and active smoker with diabetes mellitus and ischemic heart disease presented with persistent right-sided chest pain radiating to the back. Examination revealed a firm right anterolateral chest-wall mass fixed to the deep plane. Chest radiography suggested a chest-wall origin, and contrast-enhanced computed tomography demonstrated an extrapleural, lentiform mass displacing the adjacent lung without clear parenchymal invasion. CT-guided core biopsy suggested malignant peripheral nerve sheath tumor.

The patient underwent en bloc resection of the mass, including anterior portions of ribs 3-5 and involved serratus anterior muscle, followed by reconstruction using a polypropylene mesh underlay and orthogonally arranged metallic plates. Histopathology showed a malignant spindle-to-epithelioid pleomorphic neoplasm infiltrating skeletal muscle and encasing trabecular rib bone. Immunohistochemistry demonstrated diffuse vimentin and cytokeratin positivity, mild EMA expression, S100 and myogenin negativity, and focal desmin, actin, and CD68 positivity. Correlating morphology with the available immunoprofile, the resection specimen was most consistent with cytokeratin-positive UPS. The anterior margin was involved, while other margins were free.

This case highlights diagnostic pitfalls in cytokeratin-positive pleomorphic chest-wall tumors and the limitations of core biopsy. En bloc resection with rigid reconstruction is feasible, while positive margin status warrants multidisciplinary consideration of adjuvant local therapy and structured surveillance.