Necrotic lipoma at the posterior thigh mimicking liposarcoma

Abstract

A lipoma is one of the most common benign tumours and can develop at any location in the body. Lipomas present characteristic imaging features; hence, they are easy to identify on CT and MRI. However, cases of necrotic lipoma are rarely encountered; therefore, information on the imaging findings of necrotic lipomas is scarce. In the present report, we describe the case of a 63-year-old man with necrotic lipoma in the deep layer of the posterior thigh, which resembled a liposarcoma on imaging. To the best of our knowledge, only a few reports on necrotic lipoma on the extremities have been published.

Figure 1

(A) T1-weighted, (B) T2-weighted fat suppression, (C) contrast-enhanced T1-weighted fat suppression preoperative axial view, (D) T1-weighted sagittal view of MRI shows a well-demarcated round lipomatous lesion in the posterior thigh with a non-lipomatous component at the periphery of the tumour. The non-lipomatous component shows good enhancement on gadolinium administration.

Figure 2

(A) Macroscopic picture demonstrating a well-defined yellow mass, which is consistent with necrotic lipoma. (B) On histological examination, the tumour was composed of necrotic adipose tissues. Note the highly degenerative area with focal fibrosis on the left side, which is enhanced on MRI. (C) On higher magnification (square area in B), the adipose tissue in the total necrosis area shows focal cystic degeneration and fibrosis. (D) CD34 immunostaining indicates the vascular channels in the fibrous area.