Definition
A tumour in all respects resembling myxofibrosarcoma, but with an epithelioid cell component.
This is a tumour of older adult, without a gender bias.
The tumour most often occurs in or around the limb girdles. It may be subcutaneous or deep (subfascial).
The tumour is multilobated.
Tumours are not encapsulated and, in most cases, have infiltrative margins. There are both hypercellular and myxoid hypocellular areas. Within the myxoid areas, there are curvilinear vessels. The myxoid areas contain lipoblast-like cells with bubbly mucin-laden cytoplasm. There is commonly necrosis of variable extent. Mitotic rates vary between tumours, with a median of 12/10 HPF. Nuclear atypia is present and of varying extent.
The epithelioid cells are present in both the hypercellular and myxoid areas, closely mimicking undifferentiated carcinoma. They tend to form chains in the myxoid areas and are of variable extent in the hypercellular areas. They have central or eccentric round nuclei. Nucleoli are prominent. Cytoplasm is eosinophilic and may be granular. Despite the resemblance to rhabdomyoblasts, cross striations are not seen. Some cells may be multinucleate.
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2/151 |
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1/151 |
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1/131 |
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0/151 |
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The diagnosis is largely one of exclusion, with immunohistochemistry useful only to exclude other entities.
Carcinoma: may show myxoid areas
Metastatic malignant melanoma: myxoid change is very rare
Myoepithelial carcinoma
Pleomorphic liposarcoma: shows greater pleomorphism
Pleomorphic rhabdomyosarcoma
There are commonly local recurrences, retroperitoneal spread and pulmonary metastases. Despite short follow up, 5 of 14 patients died of disease.
This page last revised 26.5.2007.
©SMUHT/PW Bishop