Metastatic epithelioid sarcoma on the arm: presentation of a case report.

Epithelioid sarcoma (ES) is a highly malignant soft tissue tumor characterized by its tendency to distant metastasis, regional lymph node involvement, and recurrence. ES frequently manifests as a deep dermal mass in the distal extremities of young adults. The variety of pathological morphology makes it clinically misdiagnosed as a granuloma or rheumatoid nodule frequently. In this case, we report a new case of a 56-year-old female who was diagnosed with metastatic ES on her left upper arm. The diagnosis was confirmed by pathological biopsy and immunohistochemistry analysis, and metastatic after surgical excision. Therefore, we should implement biopsy and immunohistochemistry methods on patients to rule out rare ES.