The multiple endocrine neoplasia type 1 syndrome (MEN1) natural history is poorly evaluated, and few single-institution experiences about hereditary gastroenteropancreatic neuroendocrine tumors (GEP-NET) are reported. Our purpose is to analyze the role of GEP-NET in MEN1-related death, as well as the behavior of these lesions during follow-up. The study population consists of 77 patients diagnosed with MEN1 GEP-NET, regularly followed up since 1990. Extensive clinical data were prospectively recorded. Statistical analysis was performed both on the whole population of 77 patients and on two subgroups including patients who, during the long lasting study period, underwent GEP-NET surgery (50 pts) and who did not (27 pts), respectively. Twenty-five males (32.5%) and 52 females (67.5%) were enrolled. Sixty-four patients had MEN1 family history (83.1%), and genetic mutation was detected in 67 cases (87%). The mean age at GEP-NET diagnosis was 41.4 years (SD = 13.6); 16 patients (20.8%) had GEP-NET diagnosed before age 30 and 12 cases (15.6%) before 1996. The mean interval time between MEN1 diagnosis and GEP-NET detection was 5.7 years (range −11/37; SD = 8.1 years). Overall, the mean follow-up time from MEN1 diagnosis was 15.8 years (SD = 9.7 years) and from GEP-NET diagnosis was 9.6 years (SD = 6.9 years). Gastrinoma was the most frequent functioning GEP-NET and pancreatoduodenectomy the most adopted surgery. GEP-NET progression affected 12 patients within the non-surgical group, while 18 subjects developed progression after surgery. Our single-center data provide information on epidemiologic, clinical and pathological features of GEP-NET in MEN1 making possible to clarify their natural history.
