Clinical and pathological features of synchronous gastrointestinal stromal tumors presenting associated with other malignancies

Background: Gastrointestinal stromal tumors (GIST) are mesenchymal tumors that are believed to originate from interstitial cell of Cajal, or their related stem cells. GIST’s pathogenesis is related to sporadic kit and PDGFRa mutations. Familial GISTs (inheritable kit/PDGFRa mutations), GISTs occurring in patients with Neurofibromatosis 1 and Carnery triad are rare conditions. Over the last few years, however, few authors reported the synchronous detection of GISTs and other neoplasms in retrospective series. Aim: to investigate the incidence and clinical/pathological features of synchronous GISTs detected in patients with other malignancies. Patients and Methods: From 1999 to 2010, all GISTs detected at surgical exploration, radiological evaluation/pre-operative assessment for other malignancies were retrospectively identified in our Department’s database and selected if treated with surgical resection. Clinical and pathological features of synchronous GISTs (synch- GISTs) were retrieved and compared with primary GISTs (controls) undergone to surgical resection in the same period time. Results: 8 GISTs out of 7 patients presenting with synchronous malignancies (12.9% of all recorded GISTs), plus 54 controls were identified. M/F of patients with synch-GISTs was 6/1 vs M/F=1.25 in controls; mean age of synch-GISTs patients was 75.2 years (range:50-84) vs a mean age of 59.8 years of controls (range:27-82), p 0.0017. Within synch-GISTs group 2 patients had a gastric GIST (25%), 2 jejunal (25%), 2 ileal (25%), 1 rectal (12.55) and 1 oesophageal (12.5%), otherwise within controls gastric GISTs were the 72.2%, followed by jejunal (9.25%), duodenal (7.4%), ileal (5.6%), rectal (3.7%) and EGIST (1.85%), p<0.05. 5 synch-GISTs (62.5%) were symptomatic/incidentally detected, otherwise the remainig 3 patients presented tenesmus (rectal GIST), dysphagia (oesophageal GIST), and intestinal occlusion (1 ileal GIST); 6 patients (11.1%) within controls were asymptomatic, the remaining reported symptoms as gastrointestinal bleeding or abdominal pain (p< 0.05). Mean tumor’s diameter of synch-GISTs was 3.4 cm (range:2-6) vs a mean diameter of 7.9 cm (range:1.5-33) in controls, p 0.0001; mean mitotic index (MI)/50 HPF of synch-GISTs was 2 (range:1-5) vs a mean MI of 8.02 in controls (range 1-52), p 0.0028. All synch-GISTs were positive for kit and CD34. synch-GISTs were classified according with Miettinen’s classification resulting: 1 patient at very low risk, 4 patients at low risk, 2 intermediate risk, and 1 patient located in the high risk group. The vast majority of synchronous tumors were colorectal cancers (2 rectal, 2 sigmoid and 2 right colon cancers), plus 1 bladder carcinoma and 1 lung cancer. Mean follow-up for synch-GISTs was 17.5 months (range 3-42): 2 patients died because of the other neoplasm, the remaining are disease free. Conclusions: synch-GISTs are smaller in size, with a lower MI and occur in elderly patients, comparing with controls. synch-GISTs are usually located in the Miettinen’s low-risk groups and the prognosis seems related to the co-existing tumor rather than to the GIST. We recommend however the surgical excision of synch-GISTs in patients with other malignancies in order to define histology and to rule out a possible metastasis, since a misdiagnosis might result in an incorrect management of the other neoplasm