Fig.18.4 ).Thecellsoftenarearrayedinsmalllobuleswithinterveningfibroussepta.Alymphocyticinfiltrateusuallyispresentandmay,onoccasion,overshadowtheneoplasticcells.Seminomasalsomayelicitagranulomatousreaction.Inapproximately15%ofcases,syncytiotrophoblastsarepresent;thesecellsarethesourceoftheminimallyelevatedserumhumanchoriogonadotropin(hCG)thatisencounteredinapproximately10%ofcases.Theirpresencehasnobearingonprognosis.
Spermatocytic tumor (formerlycalledspermatocytic seminoma)isadistinctclinicalandhistologicentity.Itisanuncommontumorthatoccursinoldermenthanothertesticulartumors;affectedpatientsgenerallyarebeyond50yearsofage.Incontrastwithseminomas,spermatocytictumorslacklymphocyticinfiltrates,granulomas,andsyncytiotrophoblasts;arenotadmixedwithothergermcelltumorhistologies;arenotassociatedwithgermcellneoplasiain-situ;anddonotmetastasize.Thetumorusuallycomprisespolygonalcellsofvariablesizethatarearrangedinnodulesorsheets.
Embryonal carcinoma presentsasill-defined,invasivemassescontainingfociofhemorrhageandnecrosis(
Fig.18.5 ).Theprimarylesionsmaybesmall,eveninpatientswithsystemicmetastases.The tumor cells are large and have basophilic cytoplasm, indistinct cell borders, large nuclei, and prominent nucleoli. Theneoplasticcellsmaybearrayedinundifferentiated,solidsheetsormayformprimitiveglandularstructuresandirregularpapillae(
Fig.18.6 ).Inmostcases,cellscharacteristicofothergermcelltumors(e.g.,yolksactumor,teratoma,choriocarcinoma)areadmixedwiththeembryonalareas.Pureembryonalcarcinomasaccountforonly2%to3%ofalltesticulargermcelltumors.
Fig. 18.3 Seminomaofthetestisappearingasawell-circumscribed,pale,fleshy,homogeneousmass.
Fig. 18.4 Seminomaofthetestis.Microscopicexaminationrevealslargecellswithdistinctcellborders,palenuclei,prominentnucleoli,andasparselymphocyticinfiltrate.
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Fig. 18.5 Embryonalcarcinoma.Incontrastwiththeseminomain
Fig.18.3 ,thistumorishemorrhagic.
Yolk sac tumor isthemostcommonprimarytesticularneoplasminchildrenyoungerthan3yearsofage;inthisagegroup,ithasaverygoodprognosis.Inadults,yolksactumorsmostoftenareseenadmixedwithembryonalcarcinoma.Thesetumorsoftenarelargeandmaybewelldemarcated.Theyarecomposedoflowcuboidaltocolumnarepithelialcellsthatformmicrocysts,lacelike(reticular)patterns,sheets,glands,andpapillae(
Fig.18.7 ).Adistinctivefeatureisthepresence
Fig. 18.6 Embryonalcarcinoma.Notethesheetsofundifferentiatedcellsandprimitiveglandlikestructures.Thenucleiarelargeandhyperchromatic.
ofstructuresresemblingprimitiveglomeruli,theso-calledSchiller-Duval bodies. Thesetumorsoftenhaveeosinophilichyalineglobulescontainingα1-anti-trypsinandalphafetoprotein(AFP),whichcanbedemonstratedbyimmunohistochemicaltechniques.