Atypical lipomatous tumor/well-differentiated liposarcoma is a locally aggressive mesenchymal neoplasm composed of adipocytes and stromal cells. Gastric cases are exceedingly rare, and their malignant potential remains unclear. We report a case of a woman in her 60s who was found to have multiple submucosal tumor-like lesions of the stomach. Over time, the tumors increased in size, requiring a laparoscopic partial gastrectomy. Histological examination revealed a tumor composed of both fatty tissue and fibrous stroma with nuclear atypia. Immunohistochemistry showed positivity for CDK4 and MDM2, and fluorescence in situ hybridization confirmed MDM2 amplification, leading to a diagnosis of atypical lipomatous tumor/well-differentiated liposarcoma. This case presented an unusual gastric manifestation, with multiple submucosal tumor-like lesions on endoscopy and exhibiting progressive morphological changes over several years.
Keywords: CDK4; MDM2; atypical lipomatous tumor; stomach; well‐differentiated liposarcoma.
© 2025 The Author(s). DEN Open published by John Wiley & Sons Australia, Ltd on behalf of Japan Gastroenterological Endoscopy Society.