Pancreatic incidentalomas

Pancreatic incidentalomas are defined as asymptomatic pancreatic lesions, discovered incidentally by imaging for an unrelated indication. They are being discovered with increasing frequency as the use of high quality cross sectional imaging is becoming more widespread. These lesions cover a wide spectrum of pathology from benign simple cysts through potentially malignant lesions such as intraductal papillary mucinous neoplasia, to frankly malignant adenocarcinoma. In this article we outline the incidence, imaging characteristics and natural history of the various incidental lesions with emphasis to neuroendocrine tumors. A diagnostic approach is also suggested, including the rational use of further imaging, serum biochemistry and the utility of ultrasound guided aspiration of cyst fluid if present. We examine several proposed classification systems and discuss the role of surgery, surveillance and prognosis.

The incidental asymptomatic pancreatic lesion: nuisance or threat?

INTRODUCTION

Although asymptomatic pancreatic lesions (APLs) are being discovered incidentally with increasing frequency, their true significance remains uncertain. Treatment decisions pivot off concerns for malignancy but at times might be excessive. To understand better the role of surgery, we scrutinized a spectrum of APLs as they presented to our surgical practice over defined periods.

METHODS

All incidentally identified APLs that were operated upon during the past 5 years were clinically and pathologically annotated. Among features evaluated were method/reason for detection, location, morphology, interventions, and pathology. For the past 2 years, since our adoption of the Sendai guidelines for cystic lesions, we scrutinized our approach to all patients presenting with APLs, operated upon or not.

RESULTS

Over 5 years, APLs were identified most frequently during evaluation of: genitourinary/renal (16%), asymptomatic rise in liver function tests (LFTs; 13%), screening/surveillance (7%), and chest pain (6%). APLs occurred throughout the pancreas (body/tail 63%; head/uncinate 37%) with 48% being solid. One hundred ten operations were performed with no operative mortality including 89 resections (distal 57; Whipple 32) and 21 other procedures. Morbidity was equivalent or better than those cases performed for symptomatic lesions during the same time frame. During these 5 years, APLs accounted for 23% of all pancreatic resections we performed. In all, 22 different diagnoses emerged including non-malignant intraductal papillary mucinous neoplasm (IPMN; 17%), serous cystadenoma (14%), and neuroendocrine tumors (13%), while 6% of patients had >1 distinct pathology and 12% had no actual pancreatic lesion at all. Invasive malignancy was present 17% of the time, while carcinoma in situ or metastases was identified in an additional eight patients. Thus, the overall malignancy rate for APLs equals 24% and these patients were substantially older (68 vs 58 years; p = 0.003). An asymptomatic rise in LFTs correlated significantly (p = 0.009) with malignancy. Furthermore, premalignant pathology was found an additional 47% of the time. Seven patients ultimately chose an operation over continued observation for radiographic changes (mean 2.6 years), but none had cancer. In the last 2 years, we have evaluated 132 new patients with APLs, representing 47% of total referrals for pancreatic conditions. Nearly half were operated upon, with a 3:2 ratio of solid to cystic lesions. This differs significantly (p = 0.037) from the previous 3 years (2:3 ratio), reflecting tolerance for cysts <3 cm and side-branch IPMN. Surgery was undertaken more often when a solid APL was encountered (74%) than for cysts (32%). Some solid APLs were actually unresectable cancers. Due to anxiety, two patients requested an operation over continued observation, and neither had cancer.

CONCLUSION

APLs occur commonly, are often solid, and reflect a spectrum of diagnoses. Sendai guidelines are not transferable to solid masses but have safely refined management of cysts. An asymptomatic rise in LFTs cannot be overlooked nor should a patient or doctor's anxiety, given the prevalence of cancer in APLs.