The incidence of insulinoma in Western Sweden between 2002 and 2019

Background: Insulinoma is a rare pancreatic neuroendocrine neoplasm with an incidence of 0.7-4 cases per million/year. Because of its rarity, epidemiological studies on insulinoma are few and limited by small sample sizes. An increasing incidence of insulinoma has recently been suggested. The primary aim of this study was to investigate the incidence of insulinoma in the Västra Götaland Region (VGR) of Sweden. Secondary aims were to evaluate clinical characteristics, diagnostic workup, management and outcome in patients diagnosed with insulinoma.

Methods: Medical records were reviewed for all patients in the VGR who had received an ICD-10 diagnosis code of a benign (D13.7) and/or a malignant (C25.4) tumor in the endocrine part of the pancreas, of hypoglycemia (E.161), and/or a code of a fasting test (AB011), from 2002-2019.

Results: Forty-two patients with insulinoma were identified, 37 of whom (20 men) were residents in the VGR at the time of diagnosis, giving a mean annual incidence of 1.3 cases per million/year. The mean (±standard deviation) age at diagnosis was 56±18 years. Six of the 37 (16%) patients had metastatic insulinoma and 2 patients (5%) had a confirmed multiple endocrine neoplasia type 1 syndrome. At preoperative workup, computed tomography and endoscopic ultrasound detected an insulinoma in 28/36 (78%) and 21/21 (100%) cases, respectively.

Conclusions: Insulinoma remains a rare tumor in the modern era. The recorded mean annual incidence of 1.3 cases per million/year is compatible with the reported incidence in Sweden during the 1980s. Our results do not support an increasing incidence of insulinoma.