An 82-year-old male individual of Indian ethnicity presented with 2 weeks of bloating, nausea, and tarry black stools. Laboratory workup revealed a hemoglobin level of 10.9 g/dL, and contrast-enhanced CT of the abdomen and pelvis demonstrated gastric distention with nodular enhancement and soft tissue thickening of the gastric antrum wall with foci of ulceration (Fig 1A). Esophagoduodenoscopy showed a large, oozing, fungating mass in the gastric antrum. A follow-up fluoroscopic upper gastrointestinal series revealed a large filling defect in the gastric antrum and delayed passage of contrast material into the duodenum, suggesting partial gastric outlet obstruction (Fig 1B).
Figure 1:
Images in an 82-year-old male patient with gastric medullary carcinoma. (A) Coronal contrast-enhanced CT image of the abdomen and pelvis demonstrates irregular enhancement and thickening of the gastric antral wall (purple arrows) with focus of ulceration (red arrows). (B) Image from fluoroscopic upper gastrointestinal series shows a corresponding filling defect at the gastric antrum (yellow arrows).
The patient underwent a partial gastrectomy and omentectomy. Histopathology revealed carcinoma with enlarged cells forming trabeculae, with an interspersed background of prominent lymphoid stroma (Fig 2A). Immunohistochemical staining revealed loss of expression of the DNA repair proteins MutL homolog 1 (MLH1) and postmeiotic segregation increased 2 (PSM2) (Fig 2B), and the tumor was negative for Epstein-Barr virus (EBV) in situ hybridization. These histologic findings are consistent with a diagnosis of medullary carcinoma.
Figure 2:
(A) Photomicrograph of gastric medullary carcinoma shows sheets of cells with large nuclei and prominent cytoplasm (red arrows) with accompanying inflammatory stroma (yellow arrows). (Hematoxylin-eosin stain; original magnification, ×40.) (B) Photomicrographs for MutL homolog 1 (MLH1) and postmeiotic segregation increased 2 (PMS2) show loss of expression of both proteins in tumor cells, with retained expression in inflammatory and endothelial cells. (Immunohistochemical stain; original magnification, ×40.)
Gastric medullary carcinoma, a subtype of gastric carcinoma with lymphoid stroma, is a rare malignancy that typically manifests in older male individuals (1,2). They are relatively low stage at diagnosis, typically without extraorgan invasion or adenopathy (3). Patients often present with nonspecific symptoms related to mass effect from an obstructing tumor and anemia and melena from slow bleeding. Gastric medullary carcinomas demonstrate microsatellite instability because of loss of function of DNA repair enzymes such as MLH1 and PSM2 (4). Another subtype of gastric carcinoma with lymphoid stroma is lymphoepithelioma-like carcinoma, which is associated with EBV infection, particularly in patients from Asian countries. Due to the relatively indolent behavior of gastric medullary carcinoma, surgical resection is often curative and patients have a good prognosis. Similar to other cancers with microsatellite instability and MLH1 mutations, gastric medullary carcinoma may be sensitive to checkpoint inhibitor therapies such as the programmed cell death protein 1 inhibitor pembrolizumab, which can enhance T-cell response to cancers with high DNA mutation burden (5).
Footnotes
Funding: Authors declared no funding for this article.
Disclosures of conflicts of interest: S.G. Institutional funds for attending meetings such as the Radiological Society of North America Annual Meeting; member of the Radiology: Imaging Cancer trainee editorial board. C.W. No relevant relationships. R.G. No relevant relationships.
Keywords: Abdomen/GI, Neoplasms-Primary, Stomach
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