<prompt> In RPGN hallmark pathology is-Marked enlargement of mesangial tissueCrescent formationThickening of basement membraneAll of the above  <response>: Distinctive lesions of proliferation are called crescents owing to their shape as they fill Bowmans space. Crescents are formed both by the proliferation of parietal cells and by the migration of monocytesmacrophages into Bowmans space Ref:- Robbins book of basic pathology 10th Ed. pg 532. 