insulinoma

Digital case

 JRC:18770 : Islet cell tumor (beta cell type)

Epidemiology

Although insulinomas are very rare tumors, they are the most common pancreatic neuroendocrine neoplasms. The incidence in general population is 1-4 per 1 000000 yearly but the incidence is higher in autopsy studies.

The incidence of insulinomas in the general population is estimated 1-4 per 1 000 000 yearly. The incidence has been reported higher in autopsy studies (0.8% to 10%), suggesting that these tumors frequently remain undiagnosed.

The median age of patients at presentation is approximately 47 years, and females show a slight predominance over males (59%).

Insulinomas comprise 70% to 80% of all functional neuroendocrine pancreatic tumors.

The majority are solitary, benign lesions occurring in a sporadic setting; they are also single, small, and hypervascular, with 90% measuring less than 2 cm and 30% measuring less than 1 cm in diameter.

Approximately 10% are multiple, 10% are malignant, and 16% are associated with MEN-1 syndrome.

Malignant insulinomas tend to occur more frequently in MEN-1 patients. The incidence of insulinomas in patients with diabetes mellitus (DM) is the same with the general population.

Malignant insulinoma

See: malignant insulinoma.

It is difficult to predict the malignant nature of an insulinoma on the basis of its histological features.

The current WHO classification criteria for malignant insulinoma involve the presence of metastases, gross invasion, tumor size, percentage of mitoses, proliferative index and vascular invasion.

However, metastases are generally considered the only definitive characteristic of malignancy. Out of all insulinomas, 5%-10% are malignant.

The differential diagnosis between malignant and benign insulinomas is usually very difficult and is based on intraoperative evidence (metastases in the liver, regional nodes or local invasion), whereas in some patients the metastases are frequently found along with the recurrence of a hypoglycemic episode.

It is important to discover alternative ways of estimating the malignant potential of insulinomas and not solely rely on histopathological examination.

The combination of medical and surgical therapeutic approaches must be considered for the treatment of malignant insulinomas.

Intravenous streptozotocin chemotherapy could be administered according to published protocols (500 mg/m2 strep-tozotocin on 5 consecutive days and repeated every 6-8 weeks) and additional chemotherapy could be used according to the stage of the disease.

LOH

22q

93%

22q12.1-q12.2

unknown

11739439

Prognosis

For prognosis, see "pancreatic endocrine tumors" (PETs).

The malignancy of insulinomas is difficult to be predicted on the basis of their histological features, and the current WHO classification has been re-evaluated.

See also

 pancreatic endocrine tumors" (PETs)

References

 Pancreatic insulinoma: current issues and trends. Vaidakis D, Karoubalis J, Pappa T, Piaditis G, Zografos GN. Hepatobiliary Pancreat Dis Int. 2010 Jun;9(3):234-41. PMID: 20525548 [Free]