A 78-year-old woman was diagnosed with a proximal gastric adenocarcinoma and underwent an elective D2 total gastrectomy with splenectomy. Subsequent histopathology revealed the presence of another tumour at the gastric antrum. This was a small benign gastrointestinal stromal tumour (GIST) mixed with gastric adenocarcinoma cells similar to those of the main gastric tumour i.e. a collision tumour. The literature has only few previous reports of this very rare association. It is not known whether this synchronicity is incidental or there is a causative factor inducing the development of tumours of different histotypes in the same organ. Pathologists, oncologists and surgeons should be aware of this interesting condition.