Skeletal muscle metastasis from gastric carcinoma: a systematic review of published case reports and case series over six decades

Abstract Background Skeletal muscle metastasis (SMM) from gastric carcinoma is exceptionally rare despite the extensive vascularity and mass of skeletal muscles. The true prevalence remains unknown, and existing knowledge is limited to isolated case reports. Objective To systematically review all reported cases of SMM arising from gastric carcinoma, summarize clinical features, diagnostic approaches, imaging characteristics, treatments, and outcomes, and highlight gaps in existing literature. Methods A comprehensive literature search was conducted across PubMed, Embase, Scopus, and Google Scholar from inception to January 2025, following PRISMA guidelines. All case reports or case series describing biopsy-confirmed skeletal muscle metastasis from gastric carcinoma were included. Results A total of 31 fully documented cases were identified from 30 published studies spanning 1960–2025. Patients ranged in age from 30 to 80 years, with a male predominance. Skeletal muscle metastases most commonly involved the thigh, gluteal, paraspinal, and abdominal wall muscles. Patients typically presented with painful, enlarging intramuscular masses that were frequently misdiagnosed as abscesses or soft-tissue sarcomas. Magnetic resonance imaging (MRI) and positron emission tomography–computed tomography (PET-CT) were the most sensitive imaging modalities, while histopathological examination remained the gold standard for diagnosis. Most lesions were associated with poorly differentiated adenocarcinoma or signet-ring cell carcinoma. Survival data were available for 18 of the 31 patients; among these, the mean survival following the diagnosis of skeletal muscle metastasis was 7.7 months, with a median survival of 4.0 months (range, 0.6–30 months), indicating a poor overall prognosis. Conclusion SMM from gastric carcinoma is extremely rare but Despite its rarity, skeletal muscle metastasis should be considered in patients with gastric carcinoma presenting with new painful intramuscular masses, particularly during postoperative surveillance. Early recognition using MRI or PET-CT followed by histopathological confirmation may facilitate timely multidisciplinary management, although the prognosis remains poor.