Plexiform lesions with giant cells.

Theplexiform lesion isoneofthemoststriking histological lesions associated withpulmonary hypertension. Itisthediagnostic feature ofplexogenic pulmonary arteriopathy, thedesignation given byaworking party oftheWorldHealth Organisation1 tothat formofhypertensive pulmonary vascular disease whichmaycomplicate pre- andpost-tricuspid congenital cardiac shunts, primary pulmonary hypertension, andrarecasesof cirrhosis oftheliver andportal veinthrombosis.2 This lesion hasbeenstudied intensively andbothitshistological andultrastructural features arefamiliar tomorbid anatomists. Recently wesawahistopathological variant withgiant cells whichwassounusual astomerit report. Pulmonary vascular pathology Thelungtissue studied wasobtained atnecropsy froma womanof26years, withan aortopulmonary septal defect complicated bypulmonary hypertension, whohad undergone cardiac catheterisation. Themuscular pulmonaryarteries (100to1000,uminexternal diameter) showedmedialhypertrophy andconcentric-laminar intimal proliferation oftheonion-skin variety. There weremanyplexiform lesions composed ofdilated, sac-like branches ofpulmonary arteries inwhichhaddeveloped aplexus ofthin-walled vessels separated bysepta containing plumpcells withrounded nuclei. Insomeofthe plexiform lesions, presumed tobeolder, thesepta were thicker andfibrous. Theparent vessels showedpatchy fibrinoid necrosis whichisknowntobethebasis for thedevelopment ofplexiform lesions.3 Someoftheelastic pulmonary arteries showedcalcification anddisruption oftheir elastic laminae withsmall mineralised deposits intheintima andadventitia. Thehistology oftheplexiformlesions was unusual for, scattered amongthe anticipated cells forming theproliferation, there were large foreign bodygiant cells withmultiple nuclei (fig 1). Manyofthemhadengulfed small fragments whichwere paleblueinsections stained withhaematoxylin andeosin. Thesefragments proved tobebrightly refractile inpolarisedlight (fig 2).Fortuitous sections revealed thatthe intracellular foreign bodies werederived fromlong fibres, upto66,uminlength, withacentral linear split. Discussion