Presentation
Non-specific abdominal pain and swelling with constitutional symptoms.
Patient Data
Large hypodense soft tissue mass with cystic attenuation occupying the mid to lower abdomen. Presence of fat component (predominantly at posterior aspect), enhancing internal septations (lower aspect) and traversing vessels within. No calcifications. Anteriorly, this mass stretches and abuts the recti muscles with loss of clear fat plane in between. Inferiorly, it compresses onto the urinary bladder. It extends to the recto-vesicle pouch with no clear fat plane with the rectosigmoid colon. The mass displaces the small bowels superiorly. The descending colon is compressed posteriorly. The inferior vena cava is also compressed, however, still remains patent. The overlying peritoneum is not thickened. No peritoneal nodules seen.
Enlarged right iliac node.
Impression: Large intraperitoneal mass with fatty component, enhancing septations, local infiltration and right iliac lymphadenopathy, highly suspicious of malignancy. Liposarcoma has to be considered.
A laparotomy was done for the patient, which revealed a large solid-cystic mass with its base at the small bowel mesentery. Otherwise, the stomach, bowels, liver, and gallbladder were healthy. Approximately 10 kg of tumor was excised and sent for histopathological assessment.
Histopathology
Macroscopic description: Multiple irregular huge masses and fragments of mixed gelatinous-hemorrhagic solid tissue, blood clot, and fibrofatty tissue. Cut section showed variegated appearance with multiple hemorrhages.
Microscopic description: Mixture of uniform round to oval-shaped stromal cells and signet ring lipoblasts in a prominent myxoid stroma with delicate arborizing vasculature. In areas, the tumor is more cellular with the stromal cells appearing bizarre with highly pleomorphic vesicular nuclei, multinucleated giant cells and minimal to moderate cytoplasm. Mitosis is increased in those areas. More than half of the tumor is necrotic. The benign fatty tissue seen is separated from the tumor by thin fibrous tissue. No dedifferentiated element is observed. No lymphovascular permeation noted.
Immunohistochemical study: The cells are reactive for S100 and negative for SMA and CD34. Ki67 proliferative index is 40%.
Diagnosis: Liposarcoma, favoring high grade myxoid liposarcoma (FNCLCC Grade 3)
Case Discussion
Liposarcomas are malignant tumors of mesenchymal origin, mostly found in the subcutaneous region, extremities, and retroperitoneum. Myxoid liposarcomas are the second most common subtype of liposarcoma, most commonly occurring in the extremities 1. Primary mesenteric liposarcomas are extremely rare 2-3.
This patient had primary mesenteric myxoid liposarcoma, which is a rare location for this subtype. Myxoid liposarcoma has high water content due to the abundant myxoid matrix and appears hypodense on CT 1. In this case, the enhancing septations and traversing vessels helped to distinguish it from a benign cystic mass.
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