An unusual shoulder stiffness:: metastasis in the infraspinatus muscle as the first clinical manifestation of lung carcinoma

Purpose of the study Malignant metastases are rarely located in skeletal muscles. We report a case of lung adenocarcinoma disclosed by metastatic dissemination to the infraspinatus muscle. Case report A 66-year-old man consulted for a painful stiff right shoulder. Pain had developed progressively and did not respond to class 2 antalgesics. There was a complete loss of passive and active medial rotation while the other shoulder amplitudes were normal. A discrete tumefaction was palpated in the infraspinatus fossa. Magnetic resonance imaging alone was able to evidence an intramuscular tumoral formation within the infraspinatus. Surgical excision led to the diagnosis of metastatic adenocarcinoma of the lung and provided rapid pain relief. Nearly normal medial rotation amplitude was recovered. The patient died at 10 months from complications related to the lung adenocarcinoma. Discussion This is the first report of metastatic lung carcinoma located in the infraspinatus muscle. The clinical presentation was very exceptional, no similar cases being reported in the literature. In bloc surgical resection appears to be the best therapeutic approach, allowing positive diagnosis and relief of pain and stiffness.