Fig. 1

Photomicrographs of urothelial carcinoma in situ (CIS) and non-neoplastic urothelium (all images × 400 magnification). a-c, CIS that was equivocal on H&E (a) showing strong, transurothelial expression with AMACR (b) and CK20 (c). d-f, CIS equivocal on H&E (d) with transurothelial, moderate intensity staining with AMACR (e) and transurothelial, strong staining with CK20 (f). g-i, CIS equivocal on H&E (g) with minimal AMACR expression (h) yet transurothelial, strong CK20 expression (i). j-l, Non-neoplastic urothelium on H&E (j) with surface AMACR expression (k) and surface CK20 expression (l). m-n, Pagetoid urothelial CIS on H&E (m) showing staining of malignant cells with AMACR within a background of non-neoplastic urothelium that is negative for AMACR (n)