▁c ) ▁lower ▁rates ▁of ▁b one ▁but ▁higher ▁rates ▁of ▁soft ▁t issue ▁pl asma ▁cell ▁tum ors ▁term ed ▁pl as mac yt omas . ▁ ▁Second ary ▁P CL ▁ ▁Second ary ▁P CL ▁( s P CL ) ▁is ▁diagn osed ▁in ▁ 1 - 4 % ▁of ▁patients ▁known ▁to ▁have ▁had ▁multiple ▁my el oma ▁for ▁a ▁median ▁time ▁of ▁~ 2 1 ▁months . ▁It ▁is ▁the ▁terminal ▁phase ▁of ▁these ▁patients ▁my el oma ▁disease . ▁s P CL ▁patients ▁typically ▁are ▁highly ▁sympt om atic ▁due ▁to ▁extensive ▁disease ▁with ▁m align ant ▁pl asma ▁cell ▁in fil tr ations ▁in , ▁and ▁fail ures ▁of , ▁not ▁only ▁the ▁b one ▁mar row ▁but ▁also ▁other ▁org ans . ▁They ▁have ▁failed ▁or ▁broke ▁through ▁one ▁or ▁more ▁treatment ▁reg im ens ▁and ▁therefore ▁may ▁also ▁show ▁some ▁of ▁the ▁to xic ▁effects ▁of ▁these ▁treat ments . ▁ ▁C ause ▁P CL ▁is ▁caused ▁by ▁the ▁development ▁of ▁an ▁excess ively ▁high ▁number ▁of ▁gen etic ▁ab normal ities ▁in ▁pl asma ▁cells ▁or , ▁more ▁particularly , ▁their ▁prec ursor ▁B ▁cells ▁and ▁pl asm ab last s ▁( see ▁pl asma ▁cells ). ▁This ▁gen etic ▁inst ability ▁is ▁due ▁to ▁a ▁my ri ad ▁of ▁acquired ▁ab normal ities ▁including ▁gene ▁mut ations ; ▁single ▁nucle ot ide ▁polym orph isms ; ▁de ple t ions ▁and ▁dup lications ▁of ▁parts ▁of ▁a ▁gene , ▁larger ▁portion ▁of ▁a