Unusual skeletal muscle metastasis from gastric adenocarcinoma

Patients with gastric adenocarcinoma frequently develop hepatic metastases or peritoneal carcinosis but involvement of the skeletal muscle is extremely rare. We report the case of a 71-year-old man with a painful soft tissue mass in the right shoulder. Two years previously, the patient had been treated for a locally advanced gastric carcinoma (surgery plus chemoradiotherapy). Surgical exploration with biopsy showed skeletal muscle metastasis from the gastric adenocarcinoma in the deltoid muscle. Chemoradiotherapy resulted in complete regression of symptoms from the metastatic lesion. The patient is alive and free of recurrence in the deltoid muscle after a follow-up of 13 months. Based on this case study, the difficulty of diagnosing skeletal muscle metastases, the prognosis and treatment options are discussed.