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Occult functioning insulinomas: which localizing studies are indicated?
J A van Heerden1, C S Grant, P F Czako
1Department of Surgery, Mayo Clinic, Rochester, Minn. 55905.
Background:
An occult insulinoma refers to a biochemically proven tumor with an anatomic site that remains indeterminate before operation. The amount of radiologic localization for such patients is debatable.
Methods:
Sixty-five patients with sporadic insulinomas were surgically treated at the Mayo Clinic between January 1980 and December 1990. True occult tumors were present in 31% of these patients (n = 20). Thirty-eight negative preoperative localization studies were performed, with 10 patients undergoing more than one study. A benign adenoma was found in 19 patients when they underwent exploratory operation, whereas one patient had malignant disease with hepatic metastases. Thirteen patients underwent intraoperative ultrasonography with a 7.5 MHz real-time high-resolution transducer.
Results:
Solitary lesions were successfully removed either by enucleation or by distal pancreatectomy in all 19 patients with benign disease.
Conclusions:
This high success rate in the management of occult insulinomas suggests that extensive preoperative radiologic investigation is neither indicated nor cost-effective.