Path Quiz Case- 40
Intramuscular myxoma is a relatively uncommon benign tumour that presents as a slow growing deeply seated mass confined to the skeletal muscle.
Local surgical excision is almost always curative and recurrence is
extremely rare even in incompletely excised lesions.
It is commonly located in the large muscles of the thigh, shoulder, buttocks and rarely upper arm.
Although most cases are solitary, multiple lesions have been reported in 5% of patients.
Multiple intramuscular myxomas are rare and are usually associated with
monostotic or polyostotic fibrous dysplasia and is known as Mazabraud's
syndrome. In some patients intramuscular myxomas are associated with
Cellular myxoma (low-grade myxoid tumour with recurrent potential). This lesion has features in between intramuscular myxoma and low-grade myxofibrosarcoma.There are hypercellular areas with increased vascularity. The hypercellular areas are not associated with pleomorphism, necrosis or any mitotic activity. Cellular myxomas do not progress to higher grade lesion and they do not metastasize. There is recurrence in 5-10% cases unless excised with a clear margin.
should comment on the following:
Differential diagnosis: Visit: Myxoid Tumours of Soft Tissue
(Classically intramuscular myxoma is hypocellular, hypovascular, shows no evidence of pleomorphism or mitotic activity and the cells are S100 protein negative. Vimentin is usually positive and rarely some cells may be actin positive.)
Juxta-articular myxoma histologically resembles intramuscular myxoma but develops adjacent to large joints and involves periarticular ligaments, tendons, joint capsules and muscles. Almost 30% cases recur locally.
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