Giant Lipoma with Fat Necrosis of the Back Mimicking Atypical Lipomatous Tumor in MRI Findings

Yoshiyuki Nakamura, Yasuhir

Abstract

Background: Although fat necrosis can be observed in several inflammatory adipose diseases, the occurrence of fat necrosis in lipomas is reported to be rare. Method: A case report of fat necrosis in a lipoma mimicking atypical lipomatous tumor in MRI findings. Result: A 63-year-old man presented with a 2-year history of a subcutaneous nodule in his back. MRI showed that a 20 × 15 cm well-circumscribed tumor was located beneath the latissimus dorsi muscle with high signal intensities on both T1- and T2- weighted images and signal attenuation on fat suppression sequences. Inside the tumor, there were multiple thickened septa with gadolinium enhancement, which was consistent with atypical lipomatous tumor. However, we diagnosed this case as a lipoma with fat necrosis from the findings of an incisional biopsy and enucleation of the tumor was performed. Conclusion: A lipoma with fat necrosis may show similar imaging findings to atypical lipomatous tumor. Therefore, it is important to confirm the diagnosis histologically, when we encounter a lipomatous tumor that imaging findings indicate to be atypical lipomatous tumor. Also, we should plan to take samples of not just the adipose lesion, because the differential diagnosis may be difficult if only lipomatous regions are biopsied.