Synovial metastasis of the shoulder detected by arthroscopy as the presenting manifestation of lung adenocarcinoma

A case in which a post-traumatic shoulder impairment revealed the presence of the joint involvement by a metastatic localization of lung adenocarcinoma is presented. The patient was a 60-year-old white man, a smoker, in apparent healthy condition complaining of pain and stiffness from a 1-year-old traumatic accident to the right shoulder sustained during a tennis match. He had been unsuccessfully treated for 6 months with physical therapy. Because of the negativity of the usual imaging studies, a diagnostic arthroscopy was performed. It revealed the presence of a traumatic rupture of the glenoid labrum and of an atypical gelatinous synovial formation in the medial wall of the joint; it was histologically and immunohistochemically diagnosed as adenocarcinoma, probably originating in the lung or in the gastrointestinal tract. The pulmonary origin of the neoplasm was confirmed by computed tomography. The patient underwent chemotherapy and eventually died with contralateral lung and femur metastases 8 months after the diagnosis. The clinical importance of this rare observation is discussed.