Implications of incidentally discovered, nonfunctioning pancreatic endocrine tumors: short-term and long-term patient outcomes

Abstract

Objectives: To describe the characteristics and outcomes after resection of incidentally discovered, nonfunctioning pancreatic endocrine tumors (PETs).

Design: Case series.

Setting: Academic hospital.

Patients: Consecutive patients with an incidentally identified, nonfunctioning PET resected from May 1, 1977, through July 31, 2009.

Main outcome measures: Operative morbidity and survival after resection.

Results: A total of 139 patients with median age of 56 years (range, 21-85 years) underwent resection; tumor size ranged from 0.4 to 17.0 cm, with median size of 3.0 cm. No perioperative deaths were reported. Sixty-one patients (43.9%) experienced a perioperative complication. Twenty-six tumors (18.7%) were classified as benign, 39 (28.1%) as malignant, and 72 (51.8%) as uncertain. We were unable to confidently classify 2 tumors due to lack of information regarding mitotic rate in the pathology report. Complete follow-up was available for 112 patients (80.6%) (median, 34.2 months). Five-year actuarial survival rates were 88.8% for patients with benign disease, 92.5% for patients with tumors of uncertain biology, and 49.8% for those with malignant tumors (P = .01). Late metastasis, tumor recurrence, or disease progression were seen in 1 patient (3.8%) with tumors initially classified as benign, 8 patients (11.1%) with uncertain tumors, and 15 patients (38.5%) with tumors classified as malignant (P < .001). Of the 39 patients with tumors 2 cm or smaller, 3 (7.7%) had late metastases or recurrence. When compared with patients with symptomatic, nonfunctioning PETs, no large difference was observed in tumor size, patient age, disease, or survival.

Conclusions: Incidentally detected, nonfunctioning PETs can display aggressive behavior, even when small. Although patients with malignant disease had diminished survival and increased rates of recurrence, benign histologic findings did not eliminate the possibility of progression. Patients with incidentally discovered, nonfunctioning PETs should undergo tumor resection and careful postoperative surveillance, even if surgical pathologic findings suggest benign disease.

Figure 1

Year of resection. The 2009 column includes those patients on whom operations were performed between January 31 and July 1 only.

Figure 2

Overall survival of patients after resection of an incidentally identified, nonfunctioning pancreatic endocrine tumor (N=139). Crosshatch marks indicate date of censure.

Figure 3

Overall survival stratified by histopathologic classification after resection of an incidentally identified, nonfunctioning pancreatic endocrine tumor. Crosshatch marks indicate date of patient censure. The difference in survival between patients with benign (n=26) and malignant (n=39) lesions was statistically significant (P=.03), as was the difference between patients with uncertain (n=72) compared with benign lesions (P<.001). No significant difference in survival was found between patients with benign or uncertain lesions.

Figure 4

World Health Organization pathologic classification by tumor size. Number of tumors with each classification are shown for each size interval.

Figure 5

Overall survival from date of surgery comparing patients with incidentally identified lesions (n=139) with those with nonincidental lesions (n=30) (P=.27).