Created by HELENE MOULIN on Jul 28, 2015 4:52:39 PM, Last modified by HELENE MOULIN on Sep 30, 2015 11:41:35 AM
A 40-year-old woman presented with a painful intramuscular mass located in the medial compartment of the right thigh.
The tumour, which measured 4 cm in diameter and was haemorrhagic and cystic, was excised with surrounding muscle and the adjacent pubic ramus.
This is a relatively circumscribed intramuscular neoplasm composed mainly of rounded or ovoid cells with variable amounts of palely eosinophilic or clear cytoplasm. These cells are arranged in nests and trabeculae, focally being associated with a prominent myxoid matrix. The lesional cells have vesicular nuclei with small nucleoli and there is mild but undoubted nuclear atypia. Mitoses are infrequent. The tumour is growing in a multinodular fashion within a fibrous stroma and shows focally notably microcystic change as well as prominent stromal haemorrhage.
Immunohistochemical stains show multifocal positivity for EMA and S-100 protein, while pan-keratin, CAM 5.2, GFAP, p63 and SOX10 are negative. Staining for INI-1 is negative - i.e. lost/deleted.