Gastrointestinal stromal tumors (GISTs) may coexist with different types of malignancies, either synchronously or metachronously. The aim of this study was to characterize the clinical and histopathological features of GIST coexisting with other neoplasms.

A retrospective analysis of 76 GISTs cases diagnosed at our institution between January 2003 and March 2020 was performed. A subgroup of cases with concomitant second malignancy was selected. The clinical and pathologic records were reviewed.

18 out of 76 patients (23.7%) with GISTs were diagnosed with the second neoplasms. In 11 cases GISTs were diagnosed metachronously to the second malignancy, whereas 7 cases of GIST were synchronous. The most common concomitant neoplasms were breast cancer and gastric cancer. The concomitant GIST were located mainly in small intestine (52.6%). 14 GISTs were classified as very low or low-risk (77.8%), 3 as moderate risk (16.7%) and 1 as high risk tumors (5.6%).

The coexistence of GIST with other malignancies may be more common, than it has been considered. As the most of concomitant GISTs occurs metachronously to the second malignancy, studying of this phenomenon requires a long-term follow-up.

In recent years, increasing evidence of second neoplasms associated with gastrointestinal stromal tumors (GIST) has been found. Numerous case reports, mostly retrospective studies and a few reviews, have been published. To our knowledge, however, no systematic review or meta-analysis of the existing data has been performed so far.

To prepare a compilation, as complete as possible, of all reported second tumor entities that have been described in association with GIST and to systematically analyze the published studies with regard to frequency, localization, and types of GIST-associated neoplasms.

The MEDLINE and EBSCO databases were searched for a combination of the keywords GIST/secondary, synchronous, coincident/tumor, neoplasm, and relevant publications were selected by two independent authors.

Initially, 3042 publications were found. After deletion of duplicates, 1631 remained, and 130 papers were selected; 22 of these were original studies with a minimum of 20 patients, and 108 were case reports. In the 22 selected studies, comprising a total number of 12050 patients, an overall rate of GIST-associated neoplasias of 20% could be calculated. Most second neoplasias were found in the gastrointestinal tract (32%) and in the male and female urogenital tract (30%). The specific risk scores of GISTs associated with other tumors were significantly lower than those without associated neoplasias.

In this first systematic review, we could confirm previously reported findings of a more than coincidental association between GIST and other neoplasias. The question whether there is an underlying causal association will need further investigation. Our data suggest that even GIST with a very low risk of disease progression should prompt screening for second neoplasia and subsequent frequent controls or extended staging.