[A CASE OF SPINDLE CELL LIPOMA ARISING IN THE INGUINAL SUBCUTIS: A CASE REPORT].

A 39-year-old man was referred to us for further examination of a right inguinal mass. He had noticed the mass several months prior and had undergone positron emission tomography/computed tomography, which revealed a mass with an SUVmax of 1.48 at the right inguinal subcutis. Magnetic resonance imaging (MRI) showed a well-circumscribed, heterogeneously enhanced adipose tumor 7cm in length, adjacent to the right spermatic cord and corpora cavernosa with clear boundaries. The tumor was a suspected atypical lipomatous tumor (well-differentiated liposarcoma), and he underwent tumor extirpation surgery. At surgery, the right inguinal canal was not opened, and the right spermatic cord and corpora cavernosa were safely spared. The excised specimen was composed of lipomatous tissue macroscopically. Histopathological diagnosis was of a spindle cell lipoma. Spindle cell lipomas are relatively rare, benign tumors, comprising only 1.5% of all lipomatous tumors. They arise most commonly in the shoulder and posterior region of the neck, and rarely develop in the groin. Differential diagnosis includes atypical lipomatous tumors, but radiological diagnosis is often difficult because of similar findings on MRI. Spindle cell lipomas typically present as a subcutaneous tumor, while atypical lipomatous tumors arise in the deep layers of connective tissue. This difference in the site of the tumor may contribute to their differential diagnosis before surgery.