Synchronous occurrence of gastrointestinal stromal tumors and other primary gastrointestinal neoplasms.

To review clinical and pathologic features of Gastrointestinal stromal tumors (GISTs) occurring synchronously with other primary gastrointestinal neoplasms. Twenty-eight patients with primary GIST were treated at our institution between 1989 and 2005. Clinical and pathologic records were reviewed. The gastrointestinal stromal tumor occurred simultaneously with other primary GI malignancies in 14% of all patients with GIST. The synchronous stromal tumors were located in the stomach and were incidentally found during the operation. The coexistent neoplasms were colon adenocarcinoma, gastric cancer (2 cases) and gastric lymphoma. The synchronous occurrence of GISTs and other gastrointestinal malignancies is more common than it has been considered. The development of gastrointestinal stromal tumors and other neoplasms may involve the same carcinogenic agents.