Presentation
Lump in the right thigh noted in the last 5 months.
Patient Data
There is a deep solid tumor within the vastus medialis and intermedius muscles which show to be heterogeneously hypoechogenic compared to the adjacent muscles, with some internal vascularity.
There is a solid tumor within the anterior compartment of the thigh at the mid thigh level abutting the medial cortex of the femoral diaphysis. It is very bright on T2-weighted imaging and is low to intermediate signal on T1 imaging. Post contrast, there is irregular peripheral and incomplete central enhancement. There is edema around the lesion. The lesion is located within the vastus medialis and intermedius muscles and posteriorly bows the medial intermuscular septum. The posteromedial aspect of the tumor approaches the femoral neurovascular bundle.
Core-biopsy with posterior carbon marking of the biopsy tract was performed after discussion with surgeons.
Case Discussion
MICROSCOPIC DESCRIPTION: Sections show fragment of skeletal muscle together with fragments of dense fibrous tissue and loose myxoid fibrous tissue. The cells in the myxoid tissue are spindled or stellate, with bland oval nuclei. No mitoses are seen and there is no necrosis. In immunostains, the spindle cells are CD34+, smA+ (patchy), S100-. There is no nuclear staining for Ki67 .
DIAGNOSIS: Core biopsy of right thigh mass: Paucicellular myxoid tissue with features consistent with an intramuscular myxoma.
The patient underwent to complete local excision. The final pathology report confirmed an intramuscular myxoma with no lymphovascular or perineural invasion and showed complete excision of the thigh skin scar and carbon tract (consistent with previous biopsy site).
Case courtesy of Associate Professor Pramit Phal and Dr Beng Lim from the RMH Radiology Department.