Gastrointestinal: Glomus tumor: A rare submucosal tumor of the stomach

A 60-year-old man presented to our hospital with a submucosal tumor (SMT) of the stomach revealed by esophagogastroduodenoscopy. He had no specific complaint or previous medical history. His blood test results, including tumor marker levels, revealed no abnormalities. Esophagogastroduodenoscopy showed a 20-mm smooth, elevated lesion with an overlying normal mucosa in the greater curvature of the gastric antrum (Fig. 1a). Contrast-enhanced computed tomography images showed the gastric SMT with a clear borderline and strong enhancement (Fig. 1b). Endoscopic ultrasonography showed the hypoechoic tumor with heterogeneous echogenicity originating from the muscular propria layer (Fig. 1c). Endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) biopsy was performed, and histologic examination revealed proliferation of oval-shaped cells with clear cytoplasm and varying numbers of capillary vessels by HE staining (Fig. 1d). Although these tumor cells are morphologically similar to neuroendocrine tumor cells or epithelioid gastrointestinal stromal tumor cells, immunohistochemically the tumor cells are strongly positive for α-smooth muscle actin and negative for chromogranin A, synaptophysin, c-Kit, DOG-1, CD34, and desmin (Fig. 2). Finally, we diagnosed gastric glomus tumor. The patient underwent laparoscopic partial gastrectomy, and the histopathological findings of the resected tumor were compatible with a gastric glomus tumor without malignant findings. Glomus tumors usually occur in the peripheral soft tissues, but they have also been reported in the stomach and occasionally in the intestine. Glomus tumors in the stomach are extremely rare, accounting for nearly 1% of all gastric soft tissue tumors. Although the tumors are generally described as benign, a few reports have described gastric glomus tumors with malignant potential. Therefore, the first-choice treatment for gastric glomus tumors is surgical resection. Although immunohistochemical studies of α-smooth muscle actin are valuable for diagnosis, histologic evaluation of a gastric glomus tumor before surgery is sometimes difficult, and the tumors are often resected under a tentative diagnosis of neuroendocrine tumor or epithelioid gastrointestinal stromal tumor. EUS-FNA biopsy is a valuable minimally invasive technique to obtain an initial diagnosis of various lesions, including gastrointestinal SMTs. In our case, we achieved an accurate tissue diagnosis of gastric SMT by performing EUS-FNA with a 19-gauge needle. This case highlights that a glomus tumor should be considered as a differential diagnosis of SMTs in the stomach and that EUS-FNA could be useful for histologic examination of gastric SMTs.