Legesse T, et al. - Urothelial carcinoma cases (n = 23) were obtained and assessed for their architectural pattern and PAX8 expression. Except for one from the renal pelvis, cases were seen in the bladder. The majority (14/23) exhibited solid nests along with at least focal tubular differentiation. PAX8 immunoreactivity was strong (3+), moderate (2+), and negative in seven, six, and ten cases, respectively. Diffuse immunoreactivity was exhibited by four of the cases with strong expression and three of those with moderate staining. In four of six of cases with solid nests, eight of 14 with solid nests and tubules, and one of three with large nests, moderate-strong immunoreactivity was observed. In summary, in an important proportion of nested variant of urothelial carcinoma cases, PAX8 could be positive and identification of this finding is significant in order to circumvent misdiagnosis of nested variant of urothelial carcinoma as nephrogenic adenoma on the basis of PAX8 expression, especially in cases with tubular differentiation and limited sampling.