Endocrine Abstracts

JOINT2891

Background: Insulinomas are functioning neuroendocrine neoplasms (NENs) characterized by autonomous secretion of insulin. The incidence of insulinomas is 1-4 people per million per year which peaks in the fifth decade of life with a female preponderance. The vast majority (90%) of insulinomas are solitary, benign, pancreatic lesions with a diameter of <2 cm. Ectopic insulinomas are extremely rare (<2%), most frequently arising in peri-pancreatic or peri-duodenal regions. Extra-pancreatic NENs secreting insulin have also been described in the liver, the cervix, the kidney and the pelvis.

Case presentation: A 29-year-old woman was referred to Endocrinology Department with features of Whipple’s triad during recurrent episodes of hypoglycemia. Symptomatic hypoglycemia (glu 39mg/dl), developed twelve hours after the initiation of a 72-hour fast, with increased insulin and c-peptide levels (insulin= 60.4μIU/ml, c-peptide=4.3ng/ml). Insulin antibodies were undetectable and insulin-like growth factor 2-mediated hypoglycemia was excluded. An abdominal MRI was performed which showed a 3 cm mass at the anatomic site between the spleen, the left kidney and behind the pancreatic tail, but failed to reveal any pancreatic lesions. Further imaging with ⁶⁸Ga-DOTATATE PET/CT was in accordance with the MRI findings and showed increased radiotracer uptake (SUVmax 29.6) by the aforementioned tumor. However, on endoscopic ultrasound, a small lesion (<1 cm) in the tail of pancreas was localized in addition to the primary lesion. Ultrasound-guided fine needle aspiration was performed on both lesions and the presence of neuroendocrine neoplasmatic cells was confirmed in both the pancreatic tumor and the peri-pancreatic one. Distal pancreatectomy, splenectomy and resection of the extra-pancreatic lesion were performed. Histopathology revealed two well-differentiated, neuroendocrine neoplasms grade 2 (NEN-G2) of intermediate malignancy with a Ki-67 of 3%. Immunostaining was positive for insulin, glucagon, NSE, CD-56, synaptophysin and chromogranin. The pancreatic insulinoma measured 0.6 cm and the peri-pancreatic one 4 cm. Given that multiple insulinomas are characteristic of MEN-1 syndrome, genetic testing for menin variants was performed which was negative. Post-operative period was uneventful and during a 6-month follow-up period the patient has remained asymptomatic and euglycemic.

Conclusions: To our knowledge, this is the first report of sporadic multifocal insulinoma with both intra-pancreatic and peri-pancreatic lesions. In addition, our case emphasizes the importance of successful pre-operative insulinoma localization in order to ensure definite curative treatment.