Large gastric glomus tumour mimicking a gastrointestinal stromal tumour: a diagnostic challenge.

Gastric glomus tumour (GGT) is a mesenchymal tumour composed of modified smooth muscle cells, which is the neoplastic counterpart of perivascular glomus bodies. Preoperative diagnosis of GGT is challenging due to its clinical and imaging similarities with other common submucosal tumours, such as gastrointestinal stromal tumours (GISTs). We report a case of a woman in her early 40s with a large well-defined submucosal gastric tumour. Imaging studies and preoperative clinical diagnosis suggested GIST. Surgical resection revealed a tumour measuring 17 cm in greatest dimension, one of the largest GGTs documented in the English literature. Histopathology showed tumour cells forming nests or trabeculae and surrounding dilated thin-walled vessels. Immunohistochemistry was positive for smooth muscle actin and vimentin and negative for desmin, CD117 and DOG1, confirming a diagnosis of GGT. While most GGTs are benign, close follow-up is crucial for large tumours for early detection of recurrence or metastasis.