NEW YORK (Reuters Health) – Even when small, nonfunctioning pancreatic endocrine tumors are likely to be aggressive, and should be removed when they are discovered incidentally, according to a report in the May issue of the Archives of Surgery.

Pancreatic tumors of endocrine origin are rare, and may or may not be hormone secreting, the authors explain. Nonfunctioning tumors used not to be apparent until size or invasion caused problems, but with the widespread use of axial imaging they are now more likely to be discovered incidentally.

In the current report, Dr. Carlos Fernandez-del Castillo, at Massachusetts General Hospital in Boston, Massachusetts, and colleagues describe outcomes in a case series of 139 patients with nonfunctioning pancreatic endocrine tumors (PETs) seen over a period of 32 years, who underwent resection.

The median size of the tumors was 3 cm, and 72% were larger than 2 cm, the report indicates. The histologic classification was benign in 26 patients (18.7%), uncertain in 72 (51.8%), and malignant in 39 (28.1%) patients; classification was not possible in 2 cases.

The rate of perioperative complications such as pancreatic fistula or abscess was 43.9%, but there were no deaths, the investigators found.

Complete follow-up was available for 112 patients, for a median of 34 months. Actuarial 5-year survival rates were 88.8% in the benign group, 92.5% in those with tumors of uncertain biology, and 49.8% with malignant tumors, according to the report. Corresponding 10-year survival rates were 67.7%, 77.9% and 16.6%.

One patient with a tumor classified as benign and 8 with uncertain tumors had late metastases or recurrence, as did 3 of 39 patients with tumors less than 2 cm, the team reports.

“This study cannot demonstrate that surgical resection alters the natural history of nonfunctioning PETs or improves survival,” Dr. Fernandez-del Castillo and colleagues point out. Nonetheless, they advise, “Resection should be offered to surgically fit patients with incidentally identified PETs. No size cutoff exists beyond which malignancy can be safely excluded.”

Furthermore, they recommend “careful postoperative surveillance, even if surgical pathologic findings suggest benign disease.”

Arch Surg 2011;146:534-538.