Insulinoma is the most common pancreatic neuroendocrine tumor. Because of its diverse clinical manifestations, diagnosis is difficult.Imaging diagnosis, especially endoscopic ultrasonography(EUS) plays an important role in the diagnosis of insulinoma, with high sensitivity and specificity.Clarifying the anatomical distribution characteristics of insulinomas will help to improve the diagnostic accuracy of imaging and reduce the rate of missed diagnoses, and it will be more valuable for EUS beginners in education and training practice.

To review the clinical data of patients diagnosed with insulinoma by surgical pathology from January 1993 to November 2019 in our hospital, searching for cases with postoperative pathological diagnosis of "insulinoma" by consulting medical records.The data of the size and anatomical distribution of insulinoma are extracted to further analyze its characteristics.

A total of 116 patients were diagnosed with insulinoma including 45 males and 71 females, (13-76)years with an average age of (44.4 ± 14.85) years. There were 110 single cases of insulinoma (94.8%) and 6 multiple cases (5.2%). Location distribution: 46 cases (39.7%) were in the head and neck with 45 single cases and 1 multiple case; 68 cases were in the body and tail (58.6%) with 65single cases and 3multiple cases; in 2 pateints, multiple tumors were found in the entire pancreas (1.7%). Size of the lesion: the diameter was 0.4 ~ 3.4cm, and the average size was (1.53 ± 0.58)cm. There were 29 cases ≤1 cm, 41 cases of> 1 cm and ≤1.5 cm, 28 cases of> 1.5 cm and ≤2.0 cm, 15 cases of ≤3 cm, and 3 cases of> 3 cm. The age is related to the size of the tumor.The size of tumors for patients ≤44 years old were (1.36 ± 0.51), and that for patients>44 years old was (1.7 ± 0.6) cm, P<0.05.Tumors in the head and neck were larger than thosein the body and tail.The average size of tumors in the head and neck was (1.66±0.63)cm, and (1.42 ± 0.52)cm in the body and tail, P<0.05.

Insulinoma occurs more frequently in the body and tail of the pancreas than in the head and neck; The vast majority of tumors are single, but can be multiple distributing in the entire pancreas; Most inluslinomas are less than 1.5 cm, and the size of the tumor is related to the age of the patients and the anatomical distribution of the tumor.