Diffuse Metastasis to the Skeletal Muscle from Advanced Gastric Adenocarcinoma : A Case Report

Abstract

A 72-year-old man was referred to our department with a chief complaint of swelling of the right forearm that had persisted for two months. MRI revealed diffuse changes in the muscles with high signal on STIR images, and the patient was referred to the orthopedic department. At the time of muscle biopsy, skin tumor with redness and tenderness appeared on his left side of abdomen. Its diameter was 3 cm, height was 1.5 cm. The lesion had gently elevated margins and smooth surface. Palpation of the mass revealed elastic hard subcutaneous tumor, which adhered to epidermis but not to fascia. Biopsy was performed from the skintumor inadditionto the muscle. Histological examination of muscle and skin revealed a metastasis of poorly differentiated adenocarcinoma. Endoscopic examination of the upper gastrointestinal tract revealed intramuscular metastasis of gastric cancer. Skeletal muscular metastasis of malignant tumors is rare, and previous studies reported that the primary tumors are usually located in the lung and mammary gland. Skeletal muscular metastasis of gastric cancer is more common in male patients. The metastatic sites tend to be in the trunk, especially in the paraspinal muscles. Metastatic lesions are typically mass lesions ; however, in the present case, the changes were diffuse ; thus, it was necessary to include non-neoplastic lesions in the differential diagnosis. Skin Research, 21 : 119-125, 2022