Malignant fibrous histiocytoma (MFH) - thigh
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MRI demonstrates a large relatively well circumscribed soft tissue mass in the lateral aspect of the thigh, which has contrast enhancement and no evidence of extension into the femur.
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.
MACROSCOPIC APPEARANCE: The specimen is submitted in a single container labelled by name and "sarcoma left thigh". This is a bulky resection of muscle and skin, 15 cm long, and up to 10 x 9 cm in greatest cross-sectional dimensions. A suture denotes the superior aspect, and another suture the anterior side of the skin ellipse, the latter measuring 10 x 2.3 cm with a faint centrally placed 0.7 cm scar on the skin surface. Looking down on the specimen the skin is in the posterolateral aspect at roughly 8 o'clock. Exposed fascia lata is approximately 3.5 cm from the anterior edge of skin. 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 tumour. 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 tumour replaces and/or displaces much of the vastus musculature. The tumour 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 tumour. 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, 7.5 x 6 x 6 cm size:
- a close periosteal margin at the vastus intermedius insertion; remaining margins grossly and microscopically clear
- marked tumour radiation necrosis
- no angiolymphatic invasion identified
- excised biopsy site
Tumour appears covered in all areas, including the periosteal margin, where it is close. Only scattered islands of viable typical tumour are identified.
FINAL DIAGNOSIS: malignant fibrous histiocytoma (MFH)