Myxoid liposarcoma - thigh anterior compartment

Macroscopy: Labeled "Right anterior thigh soft tissue mass. Stitch short superior, long lateral". Tissue including muscle and fat measuring in aggregate 120 mm from superior to inferior, 170 mm from medial to lateral and the 90 mm from anterior to posterior. There is a small sliver of skin measuring 32 x 3 mm. On sectioning there is a well-defined lobulated cream/pale tan lesion measuring 155 x 95 x 84 mm. Lesion contains hemorrhage and areas suspicious for necrosis. Lesion is less than 1 mm from the inferior margin, 2 mm from superior margin, 3 mm from the anterior margin, 3 mm from the posterior margin, 2 mm from the lateral margin and 5 mm from medial margin. Inked green superior, blue posterior, black anterior/inferior.

Microscopy: Sections show a tumor arising in soft tissues but appears well circumscribed but nonencapsulated composed of varying morphology. In part the tumor is composed of closely compact area be sized deeper sites with enlarged hyperchromatic nuclei and prominent nucleoli neck and moderate numbers of lipoblast in areas there is a slightly myxoid background to the tumor and in other areas, the tumor cells show back to back pleomorphic stromal cells with very frequent mitoses and irregular nuclei and scattered intervening lipoblast. The tumor is completely excised. Lymphovascular invasion is not seen.

Conclusion:  Right anterior–myxoid liposarcoma. The lesion is completely excised. The closest margin being 1 mm from the inferior margin.

According to the FNCLCC sarcoma grading system, the histological grade is 1 of 3 (differentiation score 2, mitotic score 1, necrosis score 0). The round cell component is approximately 20% of the tumor.