Spindle cell lipoma, a rare and benign adipocytic tumor: A case report

Spindle cell lipomas are a rare, benign soft tissue mass that are easily treated with surgical excision. Although typically occurring in males and much later in life, in this case report, we present a case of a spindle cell lipoma occurring in a female teenager. The patient is a healthy 16-year-old Female who presented with a soft, mobile, and poorly defined posterior flank mass on physical exam. As it was not well-visualized by ultrasound, a magnetic resonance image (MRI) was obtained, revealing a well-defined, T1 and T2 bright, ovoid lesion in the subcutaneous tissue. On MRI, the mass measured 7.4 x 4 × 4.5 cm and was consistent with a benign fatty mass. The mass was thought to be a lipoma and it was recommended that it be excised to confirm the diagnosis. However, the patient elected to defer due to concerns about undergoing surgery. Two years later she re-presented with a much larger mass in the same region and a surgical excision was then performed. On excision, the mass appeared smooth, glistening, and fatty, measuring 13.5 x 9.8 × 4.5 cm. Histology revealed encapsulated fibroadipose tissue containing both adipocytes and CD34-staining spindle cells, consistent with a diagnosis of spindle cell lipoma. The patient continues to do well 6 months later with no evidence of recurrence. Spindle cell lipoma cannot be differentiated from lipomas pre-operatively.