Presentation
Palpated thigh mass.
Patient Data
Ultrasound reveals a well-defined very hypoechoic heterogenous lesion with detectable vascularity.
There is a well-defined fusiform mass seen in the lateral aspect of the right thigh (in the vastus lateralis muscle), it measures about 2.4 x 3.6 x 4.5 cm in TS, AP and CC dimensions and appears hyperintense signal on STIR, heterogeneously hyperintense on T2-weighted images and hypointense on T1 weighted image, with a tiny focus of blooming artifact in its lateral aspect however without diffusion restriction (not shown).
Contrast administration shows peripheral and internal linear enhancement.
Features likely suggestive of intramuscular myxoma, for pathological correlation.
Other differential includes peripheral nerve sheath tumor.
Histopathology Report
Origin of tissue: thigh (laterality not specified)
Clinical history: thigh mass
Pre-operative diagnosis: rule out intramuscular myxoma vs peripheral nerve sheath tumors
Macroscopic appearance:
Specimen received in formalin consists of 28 gm, 6 x 4 x 2 cm brownish soft tissue pieces. Sectioning reveals a 2 x 1 cm cystic-like cavity filled with colourless jelly-like material. Submitted in 5 cassettes, left tissue.
Microscopic appearance:
Sections show an intramuscular well-demarcated hypocellular myxoid nodule surrounded by thin fibrous pseudocapsule and featuring a central clear cystic space. The lesion is composed of bland cells with occasional subtle atypia and scattered rare thin blood vessels. Occasional foamy macrophages are noted. No mitotic activity is detected. The overall features are consistent with intramuscular myxoma. No evidence of malignancy is seen.
Diagnosis: intramuscular myxoma
Case Discussion
Intramuscular myxoma is a benign soft tissue tumor with no tendency to metastasize. It is mesenchymal in origin and consists mostly of myxoid matrix.
It is important to establish the diagnosis to rule out other radiologically similar tumors. The radiological characteristics of this lesion are not unique. Therefore, histopathology is crucial to differentiate it from other myxoid tumors with similar appearance.
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