A case report: Spindle cell lipoma in the floor of mouth

Abstract Spindle cell lipoma is a rare variety of lipoma that usually appears in subcutaneous tissue, for example, the posterior neck, shoulders, and back region, in middle-aged and older males. We reported a rare case of spindle cell lipoma of the floor of mouth. A 68-year-old man had a painless swelling of the floor of mouth. Clinical and image examination revealed that the mass was encapsulated, well-circumscribed, smooth-surfaced, and soft. Inside of the lesion was the same signal as adipose tissue, and the mass showed high signals at T1 and T2 weighted sequence in magnetic resonance imaging. However, the internal properties were non-uniform, and the vascular pattern was observed. Therefore, biopsy was performed before removal operation, and the mass was diagnosed as no malignancy. The encapsulated yellow mass was removed under general anesthesia. The histopathology showed that the well-demarcated mass was composed of mature adipocytes and spindle cells with bundles of collagen fibers. The size of mature adipocytes was uniform, and nuclear atypia was not observed. In immunohistochemical staining, the adipocytes were positive to S-100, and the spindle cells showed positive for CD34 and bcl-2 but S-100 negative. Based on the pathological features, the diagnosis was spindle cell lipoma. Differentiation of spindle cell lipoma includes solitary fibrous tumors, neurofibromas, subcutaneous fibrous malignancies, and well differentiated lipomas. S-100, CD34, and bcl-2 was able to differentiate these tumors and was very useful for the diagnosis of spindle cell lipoma. There were no signs of recurrence after 1-year follow up since the operation.