Pancreatic neuroendocrine tumors: radiographic calcifications correlate with grade and metastasis

Studies to identify preoperative prognostic variables for pancreatic neuroendocrine tumor (PNET) have been inconclusive. Specifically, the prevalence and prognostic significance of radiographic calcifications in these tumors remains unclear.

From 1998 to 2009, a total of 110 patients with well-differentiated PNET underwent surgical resection at our institution. Synchronous liver metastases present in 31 patients (28%) were addressed surgically with curative intent. Patients with high-grade PNET were excluded. The presence of calcifications in the primary tumor on preoperative computed tomography was recorded and correlated with clinicopathologic variables and overall survival.

Calcifications were present in 16% of patients and were more common in gastrinomas and glucagonomas (50%), but never encountered in insulinomas. Calcified tumors were larger (median size 4.5 vs. 2.3 cm, P=0.04) and more commonly associated with lymph node metastasis (75 vs. 35%, P=0.01), synchronous liver metastasis (62 vs. 21%, P<0.01), and intermediate tumor grade (80 vs. 31%, P<0.01). On multivariate analysis of factors available preoperatively, calcifications (P=0.01) and size (P<0.01) remained independent predictors of lymph node metastasis. Overall survival after resection was significantly worse in the presence of synchronous liver metastasis (5-year, 64 vs. 86%, P=0.04), but not in the presence of radiographic calcifications.

Calcifications on preoperative computed tomography correlate with intermediate grade and lymph node metastasis in well-differentiated PNET. This information is available preoperatively and supports the routine dissection of regional lymph nodes through formal pancreatectomy rather than enucleation in calcified PNET.