PANCREATIC NEUROENDOCRINE TUMORS: TUMOR SIZE, RADIOLOGIC FEATURES,
AND ASSOCIATED HIGH RISK FACTORS
Stephanie L. Koonce, M.D., Dustin L. Eck, M.D., Jeffery Farrell, John A. Stauffer , M.D.,
Horacio J. Asbun, M.D. Dept. of General Surgery, Mayo Clinic Florida, Jacksonville, FL
Background/Objective
Optimal management for small incidental pancreatic neuroendocrine tumors (PNET) may be
controversial. We sought to determine if an association existed between the size of PNET and the
presence of high-risk tumor characteristics in resected surgical specimens.
In addition, we
correlated the estimation of tumor size with preoperative imaging and compared it to final tumor
size.
Methods
A retrospective case series analysis of patients undergoing surgery for PNET at our institution
was performed. Standard statistical tests were performed to analyze relationships between final
pathologic size and high risk features as well as size of lesion on imaging.
Results
Between 1996 and 2012, 86 patients underwent 91 operations for PNET. There were 38/86
(45%) males and 48/86 (55%) females. Twenty-one, 21/86 (24%) patients had functional tumors,
9/86 (10%) familial (multiple endocrine neoplasia) tumors. On preoperative endoscopic
ultrasound and cross sectional imaging median tumor size was 1.7cm (range 0-10.5). The median
final pathologic size of the tumors was 1.8 cm (range 0.5-11). Pathologic size showed a strong
association with preoperative imaging size on all imaging modalities (r=0.86, EUS; 0.80 MRI;
0.93 CT; all p < 0.001).
High risk features include positive locoregional lymph nodes, distant
metastasis, and poorly differentiated tumors, and were present in 0/10 tumors < 1 cm, 1/28
tumors 1-1.5 cm, 4/10 tumors 1.51-2 cm, and 21/40 tumors > 2 cm respectively. Tumor size was
significantly
associated
with
the
presence
of
high-risk
features
and
recurrence
(p<0.0001;p=0.0013).
Conclusions
Increasing tumor size is strongly associated with high-risk features of PNET. Preoperative
imaging accurately predicts final pathological size of tumors. Continued aggressive management
should be favored with increasing tumor size keeping in mind even small size PNET may display
aggressive features warranting resection.
Table 1: PNET size and high risk characteristics
PNET Size
0.1-0.9 cm
(n=10)
1.0-1.5 cm
(n=28)
1.6-1.9 cm
(n=10)
>2.0 cm
(n=40)
Total
(n=88)
Poorly Differentiated
0 (0%)
0 (0%)
1 (10%)
2 (5%)
3 (3%)
Positive Locoregional
Lymph Nodes
0 (0%)
1 (4%)
1 (10%)
14 (35%)
16 (19%)
Distant Metastasis
(at time of surgery)
0 (0%)
0 (0%)
1 (10%)
6 (15%)
7 (8%)
Lympho-vascular or
Perineural Invasion
0 (0%)
0 (0%)
5 (50%)
25 (63%)
30 (35%)
1/10
(10%)
2/28
(7%)
3/10
(30%)
17/40
(43%)
23/88
(26%)
High Risk Features (%)
Tumor Recurrence
(%)