LAUSR

In contrast, the diagnosis of adenocarcinoma (which by definition is invasive because in situ lesions of the pancreas do not use the terminology of adenocarcinoma in situ) is based solely on cytologic criteria. However, when a lesion is at least partially cystic, highgrade dysplasia in pancreatic mucinous cystic neoplasms (MCNs; intraductal papillary mucinous neoplasms, mucinous cystic neoplasms, and intraductal oncocytic papillary neoplasms) enters the differential diagnosis. This distinction can be important. Although the clinical management of these 2 lesions is similar when the patient is a good surgical candidate (ie, resection), the use of, and the need for, chemotherapy and other treatment modalities (including hospice care) may differ in poor surgical candidates and depend on the presence or absence of an invasive component. Unfortunately, the current literature is neither clear nor consistent about whether or how the Papanicolaou Society criteria should be applied to partially cystic lesions. Some authors have stated that the distinction between invasive adenocarcinoma and intraductal papillary mucinous neoplasms cannot be made on cytologic material alone, and they instead have suggested that these lesions should be diagnosed as “neoplastic: neoplastic mucinous cysts with high grade atypia,” which encompasses both highgrade dysplasia and invasive adenocarcinoma. However, these same authors also state that when “frank carcinoma is identified then the case should be signed out as ‘malignant: adenocarcinoma,’” but the criteria listed for “frank carcinoma” and intraductal papillary mucinous neoplasms are virtually identical (3dimensional clusters, single cells, high nucleartocytoplasmic ratios, hyperchromasia or hypochromasia, irregular nuclear membranes, prominent nucleoli, anisonucleosis, necrosis, and intracytoplasmic vacuoles). Other authors have suggested that increased cellularity of atypical cells, necrosis, and marked anisonucleosis (including cells with nuclear size variation of at least 4:1) 12 are diagnostic of invasive adenocarcinoma. However, all of these features have been shown to be present in at least a subset of highgrade mucinous cysts. At the very least, the accuracy of the cytologic criteria for invasive adenocarcinoma is not well defined when an MCN is in the differential. An alternative approach would be to apply noncytologic criteria to the diagnosis of invasive adenocarcinoma. Indeed, this is already well established for cystic lesions on the pancreas, and the high accuracy of the current criteria for adenocarcinoma in solid masses also already relies on using imaging criteria to rule out MCNs. How far imaging criteria can be used is not clear. Some cytopathologists explicitly use their interpretation of imaging studies to alter their cytologic diagnoses in thyroid fineneedle aspiration; perhaps this approach may also be of value in the pancreas. Although molecular abnormalities (including alterations