ADRIAN STANCU, ALINA GHISE, MARIUS PENTEA, DANA EMILIA VELIMIROVICI, SORIN PASCA, LILIANA CARPINISAN,ROMEO TEODOR CRISTINA HEMATOXYLIN - EOSIN- STAINING IN A DOG POLYARTERITYS NODOSA Polyartetrtys nodosa (PAN) was diagnosed histologically in a dog 14 months old, that presented in the necropsy a hemorrhagic diathesis. The specific lesions were present in the muscular arteries of middle and small caliber and in the arterioles from heart. The modifications are segmentail, chronic, evolving from fibrinoid necrosis to the polyphasic, transmural, neutrophilic, leucocytodastic, macrophagic, lympho-plasmodtic and finally fibrotic vasculitis. The elastolisis predisposes to micro-aneurisms and micro-hemorrhages. Unlikethe perivascularitis, the inflammatory processis extended to the surrounding tissues.