18.14 ).Somevariationinnuclearsizeandshapeisusual,butingeneral,pleomorphismisnotmarked.Mitoticfiguresareuncommon.Withincreasinggrade,irregularorraggedglandularstructures,cribriformglands,sheetsofcells,orinfiltratingindividualcellsarepresent.Inapproximately80%ofcases,prostatictissueremovedforcarcinomaalsoharborspresumptiveprecursorlesions,referredtoashigh-grade prostatic intraepithelial neoplasia (HGPIN). ManyofthemolecularchangesseenininvasivecancersarealsoseeninHPIN.
Fig. 18.13 Adenocarcinomaoftheprostate.Carcinomatoustissueisseenontheposterioraspect(lower left). Notethesolidwhitertissueofcancer,incontrastwiththespongyappearanceofthebenignperipheralzoneonthecontralateralside.
ProstatecancerisgradedbytheGleason system, createdin1967andupdatedin2014.Accordingtothissystem,prostatecancersarestratifiedintofivegradesonthebasisofglandularpatternsofdifferentiation.Grade1representsthemostwelldifferentiatedtumors,andgrade5tumorsshownoglandulardifferentiation.Mosttumorsarepatterns3,4,or5.Sincethemajorityoftumorscontainmorethanonepattern,aprimarygradeisassignedtothedominantpatternandasecondarygradetothenextmostfrequentpattern.ThetwonumericalgradesarethenaddedtoobtainacombinedGleasonscore.Tumorswithonlyonepatternaretreatedasiftheirprimaryandsecondarygradesarethesame,and,hence,thenumberisdoubled.Thus,themostdifferentiatedtumorshaveaGleasonscoreof2(1+ 1),andtheleastdifferentiatedtumorsmeritascoreof10(5+ 5).AnewgradingsystemalsobasedonglandularpatternwasrecentlyacceptedbytheWorldHealthOrganization(WHO)tobeusedinitiallyinconjunctionwiththeGleasonsystem;itrangesfrom1(excellentprognosis)to5(poorprognosis).
In the United States, most prostate cancers are small, nonpalpable, asymptomatic lesions discovered on needle biopsy performed to investigate an elevated serum prostate-specific antigen (PSA) level (discussed later). Some 70% to 80% of prostate cancers arise in the outer (peripheral) glands, and a subset of these may be palpable as irregular hard nodules on digital rectal examination. A minority of carcinomas is discovered unexpectedly during histologic examination of prostate tissue removed by trans-urethral resection for BPH. Because of the peripheral location, prostate cancer is less likely than BPH to cause urethral obstruction in its initial stages. Locally advanced cancers often infiltrate the seminal vesicles and periurethral zones of the prostate and may invade the adjacent soft tissues, the wall of the urinary bladder, or (less commonly) the rectum. Bone metastases, particularly to the axial skeleton, are frequent late in the disease and typically cause osteoblastic (bone-producing) lesions that can be detected on http://ebooksmedicine.net
Fig. 18.14 (A)Adenocarcinomaoftheprostatedemonstratingsmallglandscrowdedinbetweenlargerbenignglands.(B)Highermagnificationshowsseveralsmallmalignantglandswithenlargednuclei,prominentnucleoli,anddarkcytoplasm,ascomparedwiththelarger,benigngland(top).
radionuclide bone scans.