A 73-Year-Old Man with an Incidental Diagnosis of Deltoid Intramuscular Myxoma Following a History of Trauma

Objective: Rare diseaseBackground: Intramuscular myxomas are rare and benign soft-tissue tumors of uncertain differentiation. Predisposing or precipitating factors have not yet been reported. Activating mutation in GNAS (exons 8 and 9) is detected in >90% of sporadic cases. The role of chronic myopathy, tendinopathy, or trauma to muscles in the etiology of these neoplasms is not known. We report an unusual case of a deltoid mass found following longstanding ro-tator cuff tendinopathy and a recent fall, later confirmed to be an intramuscular myxoma on biopsy.Case Report: A 73-year-old man with a 5-year history of left shoulder pain and rotator cuff tear presented with intractable pain in his left shoulder after a recent fall at home. Physical examination was suggestive of a rotator cuff injury and magnetic resonance imaging (MRI) of the left shoulder revealed a 2.7x2.5x3.7cm T1 hypo-and T2 hyperin-tense oblong mass-like signal abnormality with heterogeneous, predominantly peripheral enhancement within the deltoid muscle concerning for a malignant mass. Surgical resection was carried out along with left reverse total shoulder replacement, and histopathology revealed findings consistent with an intramuscular myxoma.Conclusions: Intramuscular myxomas are rare, benign tumors. This case report presents one such myxoma incidentally found in a patient with longstanding rotator cuff tendinopathy and a recent fall. Although this co-occurrence is likely incidental, further research and case series review of similar presentations may influence postulations of the pathophysiology of myxomas.