Background: The purpose of this study was to assess the prevalence of other neoplasms in patients with gastrointestinal stromal tumors (GISTs) and to compare clinical and histopathological data in patients with a GIST and accompanying neoplasms and in patients with GIST only.
Methods: The analysis encompassed 82 patients with a GIST from among 330 300 patients whose surgical specimens, biopsies, and autopsies were evaluated between January 1989 and June 2006. A subgroup of patients with other types of neoplasms was selected.
Results: Other neoplasms in patients with a GIST were diagnosed in 22 of the 82 (26.8%) patients. The most common accompanying neoplasms were colorectal (nine cases) and gastric (four cases) adenocarcinoma, as well as pancreatic adenocarcinoma (three cases). There was a tendency toward more common localization of a GIST in the small intestine in patients with other neoplasms than in patients with a GIST alone (P < 0.09). Tumors with very low risk of aggressive behavior were more frequent in patients with a GIST accompanied by other neoplasms than in the other group (P < 0.05). No phenotypic differences in GIST cells were found between the two groups.
Conclusions: In almost 27% of the study population, GISTs coexisted with other neoplasms. A greater proportion of patients with a GIST localized in the small intestine and/or characterized by a very low risk of aggressive behavior and accompanying other neoplasms, compared with a GIST alone, most likely reflects the fact that in the first group, GISTs tended to be an incidental finding during surgery. The results were affected by patient selection and the type of tissue material available.