Retroperitoneal Liposarcoma with Multilocular Cysts

Abstract

In this study, we describe a 60-year-old man with a giant retroperitoneal liposarcoma with multilocular cysts. He was admitted to our hospital because of a 5-month history of abdominal distention. Abdominal computed tomography revealed a giant lobulated cystic mass occupying the retroperitoneal space that contained partially solid fat components. Magnetic resonance imaging indicated that this complex mass exhibited a low signal intensity on a T1-weighted image, whereas it exhibited a high and focally intermediate signal intensity on a T2-weighted image. This patient was diagnosed with a mucinous type of retroperitoneal sarcoma, which was then resected. During surgery, the tumor was isolated from the retroperitoneum and other organs, but the detachment was required only because of fixation around the left external iliac artery. The histological diagnosis was a well-differentiated liposarcoma with multilocular cysts that contained old bloody, serous, and mucinous fluids, which are a rare phenomenon in liposarcoma. This case indicates that retroperitoneal liposarcoma should also be considered as a differential diagnosis of retroperitoneal cystic mass.

Keywords: Liposarcoma; Multilocular cysts; Retroperitoneum.

Fig. 1

CT images (a, c, axial; b, coronal). a, b A giant lobulated cystic mass that occupied the retroperitoneal space was observed and included partially solid fat components with calcification in the left portion. c Exclusion of the mass exhibited bilateral hydronephrosis. MRI images (axial). d The retroperitoneal mass demonstrated a low intensity on a T1-weighted image. e The lobulated mass demonstrated a high and focally intermediate intensity on a T2-weighted image.

Fig. 2

Macroscopic examination. a The whole tumor was encapsulated by a smooth connective fibrous capsule. b The cut surface of the tumor was composed of a multicystic and yellowish lipomatous mass that included old bloody, serous, and mucinous fluids.

Fig. 3

Microscopic examination. a The tumor consisted of mature fat, atypical lipoblasts, and mesenchymal cells. b The cyst wall was not composed of epithelial cells. c Immunostaining for S-100 shows positive tumor cells. d Immunostaining for p16 shows that the tumor cells were diffusely positive.