Objective: Clear Cell Sarcoma (CCS) is a rare tumor of mesenchymal origin accounting for 1% of soft tissue sarcomas (STS)¹. Often misdiagnosed as malignant melanoma² (MM), it has only one curative treatment: radical surgery and an extensive postoperative follow-up program². Herein, we present a case of CCS mimicking a right breast tumor, where the patient´s age, gender, growth and localization of the neoplasm render it uncommon.

Case presentation: A 70-year-old male was admitted to the Surgery Department complaining about a 3-month right breast tumor. Ultrasound evidenced a nodular formation (2.29 cm-1.91 cm) and mammography showed a hyperdense image, projected 35 mm from the nipple, surrounded by calcifications. No signs of systemic disease were present. Core needle biopsy expressed histological characteristics compatible with both MM and CCS.

Results: After multidisciplinary team meeting, a wide resection surgery was performed followed by lymphadenectomy. The immunohistochemistry and pathology report led to the diagnosis: CCS.

Conclusions: CCS is a rare sarcoma with poor prognosis. This case is exceptional due to its epidemiology, unusual clinical manifestations and appearance, setting CCS up as a new differential diagnosis to keep in mind regarding breast tumors. Its extreme rarity could help other colleagues deal with this infrequent presentation.