PMC6701358_01
MRI T1 FatSat axial showing lesion (star) within left omohyoid muscle.
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MRI showed a 5 x 2 x 4 cm ovoid mass, T1 isointense to muscle, and T2 very slightly hyperintense to muscle, embedded within the left strap musculature (Figure 1).
Gross coarsely lobulated cut surface of excised rhabdomyoma. Note: mass appears discolored due to formalin fixation.
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Since the mass was enlarging but lacked a definitive diagnosis, it was excised (Figure 2).
10x magnification of H&E stained histology specimen of rhabdomyoma shows tightly packed, variously sized, round or polygonal cells separated from one another by thin fibrous septa and small vascular channels (yellow arrows). The cells have eosinophilic, striated cytoplasm with occasional intracytoplasmic vesicles (black arrows), vacuoles (red arrows), peripherally placed vesicular nuclei, and one or two prominent nucleoli. Mitotic figures and evidence of necrosis were absent.
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Pathologic diagnosis showed skeletal muscle with rare cytoplasmic vacuoles and focal interstitial chronic inflammation consistent with extracardiac adult-type rhabdomyoma (Figure 3).