The Enigmatic Mass Over the Clavicle: A Case Report Unveiling a Rapidly Growing Spindle Cell Lipoma.

Spindle cell lipoma (SCL) is a rare, benign, adipocytic tumor typically located in the subcutaneous tissues of the neck, shoulder, and upper back regions. A 64-year-old female patient presented with a small, soft mass over her left clavicle. Her medical history included well-controlled hypertension and hyperlipidemia, and she had previously undergone an appendectomy and excision of a soft tissue cyst. On follow-up approximately one year later, the mass had demonstrated significant and rapid growth. Surgical excision of the mass revealed a 7.0x6.0x5.0 cm yellow-colored tumor, confirmed as an SCL on histopathological examination. Although benign, this case highlights the potential for rapid growth in SCLs, warranting their inclusion in the differential diagnosis when evaluating masses in the shoulder and neck region.