Rapidly progressive glomerulonephritis is stologically characterised by the presence of numerous -

RPGN is characterized by the formation of 'crescents' (crescentic GN) outside the glomerular capillaries (extracapillary GN). 'Crescents' are formed from the proliferation of parietal epithelial cells lining Bowman's capsule with contribution from visceral epithelial cells and the invading mononuclear cells. Ref: Textbook of pathology Harsh Mohan 6th edition page no: 667