Epidemiology
A rare benign tumor of adults, with a predilection for the deep muscles of the thigh, shoulder, or pelvic girdle. When there is more than one myxoid lesion or an association with fibrous dysplasia, the workup must review the whole pattern and not only the palpable mass.
Basic features
It is usually a well-defined, gelatinous mass with very high signal on MRI due to its myxoid content; when several myxomas appear together with bony fibrous dysplasia, this is called Mazabraud syndrome, which requires follow-up.
Usual treatment
It can be observed if it is typical and asymptomatic; it is resected if it grows, hurts, or cannot be confirmed with certainty. Complete removal — rather than a limited biopsy — is important, because a small sample may not represent the whole lesion and may not rule out a low-grade myxofibrosarcoma, which can resemble a myxoma.
Outcomes and prognosis
Recurrence is uncommon after complete resection, and metastatic behavior is not expected.