IPMNs continue to be recognized with increasing frequency. Five-year survival for those patients following resection of IPMNs with invasive cancer (43%) is improved compared with those patients with resected pancreatic ductal adenocarcinoma in the absence of IPMN (averages 15%-25%). Survival following resection of IPMNs without invasive cancer (regardless of degree of dyplasia) is good, but recurrent disease in the residual pancreas suggests that long-term surveillance is critical. Based on the age at resection data, there appears to be a 5-year lag time from IPMN adenoma (63.2 years) to invasive cancer (68.1 years).

Invasive pancreatic ductal adenocarcinoma is an almost uniformly fatal disease. Several distinct noninvasive precursor lesions can give rise to invasive adenocarcinoma of the pancreas, and the prevention, detection, and treatment of these noninvasive lesions offers the potential to cure early pancreatic cancers. Noninvasive precursors of invasive ductal adenocarcinoma of the pancreas include pancreatic intraepithelial neoplasias (PanINs), intraductal papillary mucinous neoplasms (IPMNs), and mucinous cystic neoplasms. Diagnostic criteria, including a distinct ovarian-type stroma, and a consistent nomenclature are well established for mucinous cystic neoplasms. By contrast, consistent nomenclatures and diagnostic criteria have been more difficult to establish for PanINs and IPMNs. Because both PanINs and IPMNs consist of intraductal neoplastic proliferations of columnar, mucin-containing cells with a variable degree of papilla formation, the distinction between these two classes of precursor lesions remains problematic. Thus, considerable ambiguities still exist in the classification of noninvasive neoplasms in the pancreatic ducts. A meeting of international experts on precursor lesions of pancreatic cancer was held at The Johns Hopkins Hospital from August 18 to 19, 2003. The purpose of this meeting was to define an international acceptable set of diagnostic criteria for PanINs and IPMNs and to address a number of ambiguities that exist in the previously reported classification systems for these neoplasms. We present a consensus classification of the precursor lesions in the pancreatic ducts, PanINs and IPMNs.

BACKGROUND: We have often encountered difficulties in identifying small liver cancers during surgery. Fluorescent imaging using indocyanine green (ICG) has the potential to detect liver cancers through the visualization of the disordered biliary excretion of ICG in cancer tissues and noncancerous liver tissues compressed by the tumor. METHODS: ICG had been intravenously injected for a routine liver function test in 37 patients with hepatocellular carcinoma (HCC) and 12 patients with metastasis of colorectal carcinoma (CRC) before liver resection. Surgical specimens were investigated using a near‐infrared light camera system. Among the 49 subjects, the 26 patients examined during the latter period of the study (20 with HCC and 6 with metastasis) underwent ICG‐fluorescent imaging of the liver surfaces before resection. RESULTS: ICG‐fluorescent imaging identified all of the microscopically confirmed HCCs (n = 63) and CRC metastases (n = 28) in surgical specimens. Among the 63 HCCs, 8 tumors (13%, including 5 early HCCs) were not evident grossly unless observed by ICG‐fluorescent imaging. Five false‐positive nodules (4 large regenerative nodules and 1 bile duct proliferation) were identified among the fluorescent lesions. Well‐differentiated HCCs appeared as uniformly fluorescing lesions with higher lesion‐to‐liver contrast than that of moderately or poorly differentiated HCCs (162.6 [71.1‐218.2] per pixel vs 67.7 [‐6.3‐211.2] per pixel, P < .001), while CRC metastases were delineated as rim‐fluorescing lesions. Fluorescent microscopy confirmed that fluorescence originated in the cytoplasm and pseudoglands of HCC cells and in the noncancerous liver parenchyma surrounding metastases. ICG‐fluorescent imaging before resection identified 21 of the 41 HCCs (51%) and all of the 16 metastases that were examined. CONCLUSIONS: ICG‐fluorescent imaging enables the highly sensitive identification of small and grossly unidentifiable liver cancers in real time, enhancing the accuracy of liver resection and operative staging. Cancer 2009. © 2009 American Cancer Society.

International experts met to discuss recent advances and to revise the 2004 recommendations for assessing and reporting precursor lesions to invasive carcinomas of the pancreas, including pancreatic intraepithelial neoplasia (PanIN), intraductal papillary mucinous neoplasm (IPMN), mucinous cystic neoplasm, and other lesions. Consensus recommendations include the following: 1) To improve concordance and to align with practical consequences, a two-tiered system (low vs. high-grade) is proposed for all precursor lesions, with the provision that the current PanIN-2 and neoplasms with intermediate-grade dysplasia now be categorized as low-grade. Thus, “high-grade dysplasia” is to be reserved for only the uppermost end of the spectrum (“carcinoma in situ” type lesions). 2) Current data indicate that PanIN of any grade at a margin of a resected pancreas with invasive carcinoma does not have prognostic implications; the clinical significance of dysplasia at a margin in a resected pancreas with IPMN lacking invasive carcinoma remains to be determined. 3) Intraductal lesions 0.5–1 cm can be either large PanINs or small IPMNs. The term “incipient IPMN” should be reserved for lesions in this size with intestinal- or oncocytic-papillae or GNAS mutations. 4) Measurement of the distance between an IPMN and invasive carcinoma and sampling of intervening tissue are recommended to assess concomitant versus associated status. Conceptually, concomitant invasive carcinoma (in contrast with the “associated” group) ought to be genetically distinct from an IPMN elsewhere in the gland. 5) “Intraductal spread of invasive carcinoma” (aka, “colonization”) is recommended to describe lesions of invasive carcinoma invading back into and extending along the duct system, which may morphologically mimic high-grade PanIN or even IPMN. 6) “Simple mucinous cyst” is recommended to describe cysts > 1 cm having gastric-type flat mucinous lining at most minimal atypia without ovarian-type stroma to distinguish them from IPMN. 7) Human lesions resembling the acinar-to-ductal metaplasia and atypical flat lesions of genetically engineered mouse models exist and may reflect an alternate pathway of carcinogenesis; however, their biological significance requires further study. These revised recommendations are expected to improve our management and understanding of precursor lesions in the pancreas.

Now that more than two decades have passed since the first reports of intraductal papillary-mucinous neoplasms (IPMNs), it has become clear that IPMN consists of a spectrum of neoplasms with both morphological and immunohistochemical variations. At a meeting of international experts on pancreatic precursor lesions held in 2003, it was agreed that a consensus classification of IPMN subtypes should be established to enable a more detailed analysis of the clinicopathological significance of the variations. Based on our experience and on information from the literature, we selected representative histological examples of IPMNs and defined a consensus nomenclature and criteria for classifying variants as distinctive IPMN subtypes including gastric type, intestinal type, pancreatobiliary type, and oncocytic type. These definitions can be used for further analyses of the clinicopathological significance of the variations of IPMN.