A Case of Gastric Atypical Lipomatous Tumor/Well-Differentiated Liposarcoma With Endoscopic Morphological Changes

Abstract

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.

FIGURE 1

Esophagogastroduodenoscopy in X‐3 reveals multiple submucosal tumor‐like elevations (8–15 mm) in the greater curvature of the stomach (A). The submucosal tumor is significantly enlarged, with the largest reaching 3 cm in diameter and showing self‐destruction at the top (B). In year X + 2 months, the ulcer at the top disappeared (C). Endoscopic ultrasonography with a 7.5 MHz convex probe reveals a hyperechoic mass in the third layer of the stomach wall (D). The tumor is indicated by an arrow, and the muscularis propria layer is indicated by an arrowhead.

FIGURE 2

A low absorption area, thought to be fat, is observed in the submucosa of the fundus of the stomach on a contrast‐enhanced computed tomography scan (A, B). A faint soft‐tissue shadow, continuous with the same area, is also visible. The excised specimen shows a yellowish fatty tissue‐like nodule under the mucosa (C, D), corresponding to the nodule that appears nodular on the endoscopic cross‐section.

FIGURE 3

A grayish‐white tissue spreads under the mucosa in the form of intervening nodules. Histologically, the yellowish part of the nodular protuberances is rich in lipomatous components under the mucosa, while the grayish‐white area between the nodules contains abundant collagen components.

FIGURE 4

Some cells are identified as lipoblasts (A). Immunohistochemistry shows that the atypical cells are CDK4‐positive (B) and weakly to strongly positive for MDM2 (C). Fluorescence in situ hybridization analysis reveals MDM2 gene amplification. The color coding of fluorescence in situ hybridization: MDM2 (Texas Red; red signal), CEN12 (FITC; green signal), DAPI (nuclear staining) (D).