Fig.13.21 ).Thisisadiscrete,compactcollectionofepithelioidcellsrimmedbyanouterzonerichinCD4+ Tcells.Itisnotuncommontoseeintermixedmultinucleategiantcellsformedbyfusionofmacrophages.Earlyon,athinlayeroflaminatedfibroblastsisfoundperipheraltothegranuloma;overtime,theseproliferateandlaydowncollagenthatreplacestheentiregranulomawithahyalinizedscar.Twoothermicroscopicfeaturesaresometimesseeninthegranulomas:(1)Schaumann bodies, laminatedconcretionscomposedofcalciumandproteins;and (2)asteroid bodies, stellateinclusionsenclosedwithingiantcells.Theirpresenceisnotrequiredfordiagnosisofsarcoidosis,andtheymayalsooccuringranulomasofotherorigins.Rarely,fociofcentralnecrosismaybepresentinsarcoidgranulomas,especiallyinthenodularform.
Thelungs areinvolvedatsomestageofthediseasein90%ofpatients.Thegranulomaspredominantlyinvolvetheinterstitiumratherthanairspaces,withsometendencytolocalizeintheconnectivetissuearoundbronchiolesandpulmonaryvenulesandinthepleura(“lymphangitic”distribution).ThebronchoalveolarlavagefluidcontainsabundantCD4+ Tcells.In5%to15%ofpatients,thegranulomaseventuallyarereplacedbydiffuse interstitial fibrosis, resultinginaso-called“honeycomblung”.
Fig. 13.21 Sarcoid.Characteristicperibronchialnoncaseatinggranulomaswithmanygiantcellsarepresent.
Intrathoracichilar and paratracheal lymph nodes areenlargedin75%to90%ofpatients,whileone-thirdpresentwithperipherallymphadenopathy.Thenodesarecharacteristicallypainlessandhaveafirm,rubberytexture.Unlikeintuberculosis,lymphnodesinsarcoidosisare“nonmatted”(nonadherent)anddonotulcerate.
Skin lesions areencounteredinapproximately25%ofpatients.Erythema nodosum, thehallmarkofacutesarcoidosis,consistsofraised,red,tendernodulesontheanterioraspectsofthelegs.Sarcoidalgranulomasareuncommonintheselesions.Bycontrast,discretepainlesssubcutaneousnodulescanalsooccurinsarcoidosis,andtheseusuallyrevealabundantnoncaseatinggranulomas.
Involvement of the eye and lacrimal glands occurs in about one-fifth to one-half of patients. Theocularinvolvementtakestheformofiritis oriridocyclitis andmaybeunilateralorbilateral.Asaconsequence,cornealopacities,glaucoma,and(lesscommonly)totallossofvisionmaydevelop.Theposterioruvealtractalsoisaffected,withresultantchoroiditis, retinitis, andoptic nerve involvement. Theseocularlesionsarefrequentlyaccompaniedbyinflammationinthelacrimalglands,withsuppressionoflacrimation(sicca syndrome). Unilateral or bilateral parotitis with painful enlargement of the parotid glands occursinlessthan10%ofpatientswithsarcoidosis;somegoontodevelopxerostomia(drymouth).CombineduveoparotidinvolvementisdesignatedMikulicz syndrome.