A Rare Presentation of Gastric Plexiform Fibromyxoma: Diagnostic Challenges and Surgical Management

A 59-year-old female presented to the hospital with acute abdominal pain. She reported a six-month history of melena, early satiety, postprandial fullness, unintentional weight loss, and loss of appetite. Contrast-enhanced CT of the abdomen revealed an exophytic mass in the antropyloric region, measuring approximately 4.2 cm. Ultrasonography showed a large ulceroproliferative lesion in the gastric antrum. The patient subsequently underwent a subtotal gastrectomy. The resected specimen measured 13 cm along the greater curvature and 7.5 cm along the lesser curvature. Gross examination of the serosal surface revealed a nodular area near the greater curvature. On cut section, a well-defined submucosal lesion measuring 3.5 × 3 × 1.9 cm with intact overlying mucosa was identified. The lesion appeared gray-white and firm and exhibited a characteristic whorled pattern, extending into the muscularis propria. A PET-CT scan revealed mild hepatomegaly with hepatic cysts, along with renal calculi in the right kidney. Histopathological examination of the lesion was followed by immunohistochemical analysis. The tumor cells tested negative for CD117, anaplastic lymphoma kinase, and pan-cytokeratin and positive for smooth muscle actin, vimentin, and desmin. The Ki-67 proliferation index was low, estimated at 10%. These findings were consistent with a diagnosis of plexiform fibromyxoma, a rare benign gastric mesenchymal tumor.