Abstract
We treated a patient with spindle cell lipoma (SCL) mimicking well-differentiated liposarcoma (WDLS) because of rapid growth. A 67-year-old man had noticed a soft tissue mass at the nape two years previously. At the first visit, a soft tissue tumor, measuring 4×4cm, was palpable at the nape. From the MR findings and the location, SCL was suspected. He re-visited us 1 year and 6 months later. The tumor enlarged, measuring 10×9cm, and WDLS was suspected. MR imaging showed mixture of high and iso-intensity areas on T1-weighted images, and high intensity on T2-weighted images, suggesting mixture of lipomatous and non-lipomatous areas. The latter area was strongly enhanced by contrast medium. Tentative diagnosis of core-needle biopsy was atypical lipomatous lesion, suggesting WDLS. Therefore, wide excision was performed.
Histologically, the tumor consisted of mature adipose tissue and spindle cells. Immunohistochemically, spindle cells were positive for CD34. From these findings, we diagnosed as SCL. No local recurrence occurred 17 months after surgery. Although MR examination and needle biopsy were performed on this patient, we could not differentiate SCL from WDLS. In this case, incisional biopsy should have been performed for accurate preoperative diagnosis.
