Metastatic leiomyosarcoma manifesting as a gastric erosion: an uncommon clinical presentation

A 75-year-old man presented with profound fatigue, hypoxia, and life-threatening anemia (hemoglobin, 4 g/dL), requiring multiple red blood cell transfusions. Contrast-enhanced chest computed tomography demonstrated segmental pulmonary embolism, extensive left-leg deep vein thrombosis, and a 30×20-mm subpleural nodule with moderate enhancement (Fig. 1). Esophagogastroduodenoscopy revealed a solitary, round, 4-mm-sized antral ulcer with sharply demarcated, mildly elevated margins, a shallow whitish-fibrinous floor, and a narrow erythematous rim that was atypical for simple erosion (Fig. 2). Given the morphology, severe unexplained anemia, and concomitant thoracic mass, we performed targeted biopsies. Histology revealed an atypical spindle-cell proliferation with a Ki-67 index of 10%, strong desmin and smooth-muscle-actin immunoreactivity (Fig. 3); hematoxylin and eosin staining at ×200 showed spindle cells with eosinophilic cytoplasm, marked pleomorphism, hyperchromasia, and irregular nuclear contours (Fig. 4). Endoscopic ultrasonography confirmed preserved wall stratification without perigastric adenopathy. Whole-body fluorodeoxyglucose positron emission tomography/computed tomography demonstrated intense uptake in the subpleural nodule (SUVmax, 8.7) and additional hyper-metabolic foci in the mediastinal and right axillary lymph nodes, indicating systemic spread rather than isolated gastric involvement. Endobronchial ultrasound-guided needle biopsy of the pulmonary lesion confirmed high-grade leiomyosarcoma with smooth muscle differentiation (AML+++, desmin++; focal caldesmon positivity). Thus, the gastric ulcer was secondary to metastatic leiomyosarcoma; consequently, curative surgery was precluded, and systemic therapy was initiated. Biopsy showing a neoplasm composed of spindle-cell proliferation with abundant eosinophilic cytoplasm and severe diffuse atypia with significant pleomorphism in the form of hyperchromasia, high nucleus-to-cytoplasm ratio, and irregular nuclear contours, arranged in intersecting storiform and haphazard patterns (hematoxylin and eosin, ×200). Leiomyosarcomas are aggressive mesenchymal neoplasms that rarely seed in the gastrointestinal tract and may mimic primary gastric cancer.1 Autopsy series identify gastric deposits in only 1.7% to 5.4% of advanced cancers, predominantly breast, lung, or esophageal, with poor outcomes despite occasional palliative resection.2 Most reported gastric metastases appear as submucosal nodules or small plaques. Our case broadens this spectrum by showing that even a minute antral ulcer can conceal metastatic leiomyosarcoma, emphasizing the need for meticulous multimodal assessment, as apparently benign lesions may conceal highly aggressive disease.