Collision of adenocarcinoma and gastrointestinal stromal tumour in the stomach: a case report

Abstract

Objective Gastric adenocarcinoma may coexist with another synchronous tumour of different histological type in another part of the stomach. Rarely, cells of different histological types may intermix and form a collision tumour. We present a very rare case of gastric collision tumour consisting of gastrointestinal stromal tumour (GIST) and adenocarcinoma. Case report A total gastrectomy of a 67-year-old man, on gross examination showed excavated cancer, 6.2 cm diameter, located in the lesser curvature. A nodule of firm white tissue, 5 cm diameter, was present on the external surface of the lesser curvature closely juxtaposed to the adenocarcinoma. The nodule revealed morphology of gastrointestinal stromal tumour with low malignant potential, which had arisen from muscularis propria. It was composed of spindle cells positive for CD117, CD34 and S-100, but negative for actin and cytokeratin. An additional finding was the presence of numerous cytokeratin positive gastric carcinoma cells and glands in between the peripheral parts of the GIST. Conclusions It is not known whether or not this association is a simple incidental coexistence or whether the two lesions are connected by a causal relationship. It has been hypothesized that the same carcinogen may induce simultaneous proliferation of different cell lines, i.e., epithelial and stromal cells.