Chest Wall Clear Cell Sarcoma: A Rare Presentation of an Uncommon Melanocytic Soft Tissue Sarcoma

Background: Clear cell sarcoma (CCS) is a rare and aggressive soft tissue sarcoma characterized by melanocytic differentiation. While it typically arises in the deep soft tissues of the extremities, its occurrence in the chest wall is exceedingly uncommon. Case Presentation: We report a 55-year-old male who presented with a gradually enlarging painless mass over the left posterior chest wall. PET-CT revealed an FDG-avid mass involving the 8th and 9th ribs. The patient underwent wide local excision with en bloc rib resection achieving clear margins. Histopathology revealed nests and fascicles of clear-to-eosinophilic epithelioid and spindle cells with melanin pigment. Immunohistochemistry showed diffuse positivity for S-100, SOX10, HMB-45, and Melan-A, consistent with clear cell sarcoma.Conclusion: Chest wall CCS is extremely rare and can pose diagnostic challenges due to overlap with malignant melanoma. Recognition of characteristic histomorphology and immunophenotype is essential. Complete surgical excision with clear margins remains the cornerstone of treatment, and long-term surveillance is necessary due to the risk of recurrence and metastasis.