AMACR and microscopic polyangiitis: Though MPA and papillary adenoma both exhibit similar microscopic characteristics, the two can be differentiated by the more prominent stromal component in MPA, compared to the more epithelioid appearance of papillary adenoma, in addition to positivity for CK7, AMACR and vimentin in papillary adenoma, which are all negative in pleomorphic adenoma [17].