Lesions of Ductal Morphology in the Prostate

To the Editor.—During the last few decades, lesions with ductal morphology in the prostate have raised considerable controversy. This includes the distinction of a subset of lumen-spanning neoplastic proliferations within distended prostatic ducts from the more common forms of high-grade prostatic intraepithelial neoplasia (eg, those with tufted, micropapillary, and flat architecture) and the separate categorization of ductal adenocarcinoma of the prostate. In their recent authoritative review of the subject, 4 eminent urogenital pathologists1 make a proposal on the reporting of these lesions in pathologic practice. Strikingly, the outcome of their analysis is largely in line with another review on the same topic.2 Both reviews recommend reporting intraductal carcinoma as a separate entity based on (1) the feasibility of defining histopathologic criteria that allow its distinction from high-grade prostatic intraepithelial neoplasia and adenocarcinoma and (2) its unfavorable clinical impact as compared to high-grade prostatic intraepithelial neoplasia. Furthermore, both reviews propose to include intraductal carcinoma identified in a prostate biopsy specimen in the Gleason score (as grade 4 or 5) in the rare event that prostate core biopsy specimens contain grade 3 carcinoma associated with intraductal carcinoma, resulting in at least a Gleason score 7. Although Gleason himself failed to separate intraductal carcinoma (cribriform or comedo-type) from invasive carcinoma, the recognition of intraductal carcinioma would not impact the Gleason grading system.The review by Cohen et al3 is somewhat contradictory with regard to their recommendation of repeat biopsies in the rare instance of an isolated intraductal carcinoma identified in prostate biopsy specimens. At one point the authors suggest that this finding should immediately lead to a radical prostatectomy without further exploration for the presence of invasive carcinoma. In their final recommendations, however, an early repeat biopsy is recommended. In our opinion the latter would be advised, as it seems that occasionally intraductal carcinoma may not be associated with invasive disease.3 It may otherwise be difficult to explain to the urologist and patient after radical prostatectomy that major surgery was performed for noninvasive disease.A difference in opinion seems to emerge from the point of view of Cohen et al that ductal adenocarcinoma can be superseded by the unifying term intraductal carcinoma of the prostate.1 There is indeed no clear reason to consider ductal adenocarcinoma as a separate category of prostatic adenocarcinoma, as proposed in the World Health Organization classification of prostate tumors,4 since it is generally associated with conventional (acinar) adenocarcinoma. In our opinion, ductal adenocarcinoma should be considered as a variant of prostatic adenocarcinoma, much as mucinous and clear cell carcinomas are considered variants. There are sound morphologic and clinical reasons for this view: (1) its characteristic morphology, particularly the tall columnar cell type lining true papillary formations; (2) the urinary obstructive symptoms if located centrally within the prostate; and (3) its identification late in the disease course as a consequence of the slow rise in prostate-specific antigen levels. Similar to the situation with all other adenocarcinomas, we do not see any reason to categorize the ductal adenocarcinomas within the group of intraductal carcinomas, given their generally evident invasive character.

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