Insulinoma: a multicenter, retrospective analysis of three decades of experience (1983-2014).

Objective: To analyze the clinical features, diagnostic procedures, treatment, and clinical outcome of insulinomas diagnosed and treated in the period 1983-2014 in four Spanish hospitals.

Methods: All patients with either biochemical and morphological criteria of insulinoma and/or histological demonstration of insulin-secreting tumor were included.

Results: Twenty-nine patients [23 women (79.3%); mean age 48.7±17.4 years (range, 16-74)] were recruited. Twenty-six patients (89.7%) had sporadic tumors, and the rest (3 women, 10.3%) developed in the context of multiple endocrine neoplasia type 1. There were 3 (10.3%) multiple insulinomas, one associated with multiple endocrine neoplasia type 1, and two (6.9%) malignant insulinomas, both sporadic. Most patients (n=18, 62.1%) had fasting hypoglycemia, about a third (31%) both postprandial and fasting hypoglycemia, and 6.9% postprandial hypoglycemia only. Time to glucose nadir (37.3±6.5mg/dL) in the fasting test was 9.0±4.4h, with maximal insulin levels of 25.0±20.3μU/mL. Abdominal CT detected insulinoma in 75% of patients. Twenty-seven (93.1%) patients underwent surgery [enucleation, 18 (66.7%) and subtotal pancreatectomy, 9 (33.3%); tumor size, 1,7±0,7cm]. Surgery achieved cure in the majority (n=24, 88.9%) of patients.

Conclusion: In our setting, insulinoma is usually a benign, small, and solitary tumor, mainly affecting women aged 45-50 years, and usually localized with abdominal CT. The most commonly used surgical technique is enucleation, which achieves a high cure rate.