Collagen bands,whichdividetheinvolvedlymphoidtissueintocircumscribednodules(
Fig.12.22 ).Thefibrosismaybescantorabundantandthecellularinfiltratecontainsvaryingproportionsoflymphocytes,eosinophils,histiocytes,andlacunarcells.
Mixed-cellularity Hodgkin lymphoma isthemostcommonformofHodgkinlymphomainpatientsolderthan50yearsofageandcomprisesabout25%ofcasesoverall.Thereisamalepredominance.Classic RS cells are plentiful withinaheterogeneousinflammatoryinfiltratecontainingsmalllymphocytes,eosinophils,plasmacells,andmacrophages(
Fig.12.23 ).Thissubtypeismorelikelytobedisseminatedandtobeassociatedwithsystemicmanifestationsthanthenodularsclerosissubtype.
Lymphocyte-predominant Hodgkin lymphoma,accountingforabout5%ofcases,ischaracterizedbythepresenceoflymphohistiocytic (L&H) variant RS cells thathaveadelicatemultilobed,puffynucleusresemblingpoppedcorn(“popcorncell”).L&HvariantsusuallyarefoundwithinlargenodulescontainingmainlysmallBcellsadmixedwithvariablenumbersofmacrophages(
Fig.12.24 ).Otherreactivecells,suchaseosinophils,arescantyorabsent,andtypicalRScellsarerare.UnliketheRSvariantsin“classical”Hodgkinlymphoma,L&HvariantsexpressBcellmarkers(e.g.,CD20)andusuallyfailtoexpressCD15andCD30.Mostpatientspresentwithisolatedcervicaloraxillarylymphadenopathy,andtheprognosistypicallyisexcellent.
ItisapparentthatHodgkinlymphomaspansawiderangeofhistologicpatternsthatoftensimulateareactiveinflammatoryprocess.Regardlessofsubtype,the diagnosis rests on the definitive identification of RS cells or variants in the appropriate background of reactive cells. ImmunophenotypingplaysanimportantroleindistinguishingHodgkinlymphomafromreactiveconditionsandotherformsoflymphoma.Inallsubtypes,involvementofthespleen,liver,bonemarrow,andotherorgansmayappearinduecourseandtakestheformofirregularnodulescomposedofamixtureofRScellsandreactivecells,similartowhatisobservedinlymphnodes.
Fig. 12.23 Hodgkinlymphoma,mixed-cellularitytype—lymphnode.Adiag-nostic,binucleateReed-Sternbergcellissurroundedbyeosinophils,lympho-cytes,andhistiocytes.(Courtesy of Dr. Robert W. McKenna, Department of Pathology,University of Texas Southwestern Medical School,Dallas,Texas.)
Fig. 12.24 Hodgkinlymphoma,nodularlymphocyte-predominanttype—lymphnode.Numerousmature-lookinglymphocytessurroundscattered,large,pale-staininglymphocyticandhistiocyticvariants(“popcorn”cells).
(Courtesy of Dr. Robert W. McKenna, Department of Pathology, University of Texas Southwestern Medical School, Dallas,Texas.) http://ebooksmedicine.net
The origin of RS cells remained mysterious through most of the 20th century, but was finally solved by elegant studies performed on single microdissected RS cells. These showed that every RS cell from any given case possesses the same immunoglobulin gene rearrangements and that these rearranged immunoglobulin genes have undergone somatic hypermutation. As a result, it is now agreed that