PMC10176190_01
Mazabraud syndrome: MRI aspects. a Coronal MRI showing three intramuscular lesions (myxoma). Left, T1-weighted sequence with homogeneous hyposignal (red stars). Middle, T2-weighted sequence with slightly heterogeneous hypersignal of the biggest lesion (red star). Right, T1 Fat-Sat gadolinium sequence with heterogeneous highly enhancement of the three lesions (red stars). b Coronal MRI showing both one bone fibrous dysplasia (green star) and one intramuscular myxoma (red star). Left, T1-weighted sequence with homogeneous hyposignal of both lesions. Middle, T2-weighted sequence with heterogeneous hypersignal of both lesions. Right, T1 Fat-Sat gadolinium sequence with highly heterogeneous enhancement of both lesions. Both intramuscular tumor and bone tumor are located in the same anatomical region and without any continuity.
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August 2020, the patient, a 52-year-old man, consulted his general practitioner after autopalpation of a mass located on the posterior side of the left thigh associated with pain. A magnetic resonance imaging (MRI) of the left thigh revealed several homogeneous muscular lesions with heterogeneous enhancement after injection, the largest of which was in the left gluteus medius muscle, measuring 70 x 40 mm, two other lesions in the left gluteus maximus muscle measuring 27 and 32 mm, respectively, and a 4th lesion along the long head of the left biceps femoris muscle measuring 48 mm (Fig. 1).
Mazabraud syndrome: FDG-PET scan aspects. a Transversal FDG-PET scan showing an homogeneous hypodense intramuscular myxoma (left: red star), with a moderated FDG uptake (right: red arrow). b Transversal FDG-PET scan showing an homogeneous hypodense intramuscular myxoma (left: red star) and a bone fibrous dysplasia (middle: heterogeneous lytic lesion - green star), with a moderate FDG uptake of both lesions (right: red and green arrows, respectively).
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F-18 fluorodeoxyglucose-positron emission tomography (FDG-PET) demonstrated a moderated uptake in all soft tissues tumors and bone lesions, with a maximum standardized uptake value equal to 3 (Fig. 2).
Myxoma in a Mazabraud syndrome: pathological aspects. a At low power field, the tumor was hypocellular, composed of spindle cells, dispersed in a myxoid stroma. b At higher magnification, cells are bland, with no atypia and no mitotic activity. There was no necrosis, no lipoblasts, and scant blood vessels. c By immunohistochemistry, the proliferation index Mib1 was very low (<2%). Two positive cells are indicated with arrows.
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Analysis revealed a spindle cell tumor with myxoid stroma (Fig. 3). This lesion was hypocellular, composed of bland spindle cells, with no atypia, no mitotic activity (Fig. 3a, b), and a very low proliferation index Mib1 by immunohistochemistry (Fig. 3c).