Malignant fibrous histiocytoma (MFH) - thigh

Discussion:

This 80-year-old male has a typical appearing malignant fibrous histiocytoma (MFH), although the imaging appearances themselves are relatively non-specific and could represent any number of sarcomas. 

The patient went on to have a resection. 

Pathology

MACROSCOPIC APPEARANCE:  The specimen is a bulky resection of muscle and skin, 15 cm long, and up to 10 x 9 cm in greatest cross-sectional dimensions. A 2 cm zone of unremarkable fat is interposed between the skin and the fascia lata anteriorly and between the skin and biceps muscle posteriorly. A 4 x 3 cm portion of gluteus maximus is present superiorly. The profunda vessels are tied in this region. The tumor has been detached from the femur along with periosteum, and the vastus muscles transected anterior to the tumor. A soft movable layer consistent with sciatic epineurium is present anterior to the biceps femoris muscle. 

On section, a firm white to light tan fibrotic tumor replaces and/or displaces much of the vastus musculature. The tumor is up to 6 x 6 cm in greatest cross-sectional dimension, spanning a length of 7.5 cm. Scattered islands of fatty tissue are noted within the tumor. It abuts the periosteum, biceps muscle, sciatic epineurium, fascia lata and adjacent subcutaneous tissue. It appears covered in all locations, coming within 0.7 cm of the subcutaneous tissue margin posteriorly and anteriorly. It is 3.5 cm from the superior margin, and 2 cm from the inferior.

MICROSCOPIC APPEARANCE: Left posterior/lateral thigh skin and soft tissue resection showing high grade malignant fibrous histiocytoma, pleomorphic/storiform type, arising in the lateral muscle compartment. Marked tumor radiation necrosis. No angiolymphatic invasion identified. Excised biopsy site.

Tumor appears covered in all areas, including the periosteal margin, where it is close. Only scattered islands of viable typical tumor are identified. 

FINAL DIAGNOSIS: malignant fibrous histiocytoma (MFH)

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