Context.-The pancreas gives rise to an array of distinct neoplasms that can be solid, cystic, or intraductal and can recapitulate the various lines of differentiation present in the normal gland. Objective.-To develop an algorithmic approach to the diagnosis of pancreatic neoplasms that simplifies their pathologic evaluation. Data Sources.-We reviewed literature related to the classification of pancreatic neoplasms on the basis of their gross, histologic, and immunohistochemical features. Conclusions.-By using a series of dichotomous decisions, the differential diagnosis of a pancreatic neoplasm can be narrowed, and in cases of the more common neoplasms, accurate classification can be achieved. Uncommon neoplasms not accounted for by this approach are also discussed, and the additional diagnostic information needed for complete pathologic reporting is presented.
An Algorithmic Approach to the Diagnosis of Pancreatic Neoplasms David S. Klimstra, MD; Martha B. Pitman, MD; Ralph H. Hruban, MD ● Context.—The pancreas gives rise to an array of distinct Conclusions.—By using a series of dichotomous deci- neoplasms that can be solid, cystic, or intraductal and can sions, the differential diagnosis of a pancreatic neoplasm recapitulate the various lines of differentiation present in can be narrowed, and in cases of the more common neo- the normal gland. plasms, accurate classiﬁcation can be achieved. Uncom- Objective.—To develop an algorithmic approach to the mon neoplasms not accounted for by this approach are diagnosis of pancreatic neoplasms that simpliﬁes their also discussed, and the additional diagnostic information pathologic evaluation. needed for complete pathologic reporting is presented. Data Sources.—We reviewed literature related to the (Arch Pathol Lab Med. 2009;133:454–464) classiﬁcation of pancreatic neoplasms on the basis of their gross, histologic, and immunohistochemical features. T o help classify pancreatic neoplasms, we have devel- oped a simple diagnostic algorithm that integrates the gross and radiographic features with the histologic and pancreatic neoplasms are inﬁltrating ductal adenocarci- nomas or closely related variants thereof (see below).2 The other more commonly encountered entities each make up immunohistochemical ﬁndings. By following the steps de- no more than 1% to 5% of pancreatic neoplasms, but since tailed in this review, the pathologist can accurately classify the latter entities include the most treatable (or even cur- most pancreatic neoplasms, although some exceptions do able) neoplasms to arise in the pancreas, their proper rec- occur, either because the rarity of a neoplasm would ren- ognition and separation from ductal adenocarcinoma is der the algorithm overly complex if it were included, or very important. because some common neoplasms rarely demonstrate un- The classiﬁcation of pancreatic neoplasms is based in usual features. Nonetheless, this conceptual approach can large part on their gross conﬁguration (solid, cystic, intra- help delineate the interrelationships among entities and it ductal) and the lines of cellular differentiation they exhibit can advance our understanding of the fundamental fea- (ductal, acinar, endocrine).3 Based upon the histologic fea- tures that deﬁne each entity. tures (especially in the case of ductal differentiation), the differentiation present in a pancreatic neoplasm may be THE BASIS FOR CLASSIFYING evident, but in some circumstances additional studies are PANCREATIC NEOPLASMS needed (Table 3). Pancreatic epithelial neoplasms exhibit a wide range of Direction of Differentiation pathologic features. The current classiﬁcation of pancreatic The most common direction of differentiation observed epithelial neoplasms is listed in Table 1.1 Of course, some in pancreatic neoplasms is toward a ductal phenotype. of the entities included are very uncommon or are regard- Ductal differentiation is deﬁned as the recapitulation of the ed as variants of other entities from which they do not characteristics of normal ducts, that is, gland or tubule differ signiﬁcantly in terms of treatment or prognosis. formation and mucin production.3 Mucin can be demon- Thus, this extensive classiﬁcation schema can be con-
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