Variant morphology in upper urinary tract urothelial carcinoma: a fourteen-year case series of biopsy and resection specimens

Upper urinary tract urothelial carcinoma exhibiting variant morphology, especially in higher-grade tumors, is a recognized phenomenon but has not been comparatively studied in biopsy versus resection material. We studied the morphologic patterns and clinicopathological features, and provide a comparison between biopsy and resection specimens. Consultation cases were evaluated separately to investigate for possible consultation bias. A total of 383 in-house cases from 352 patients including 314 resection specimens and 69 biopsies from 2001-2014 were reviewed from a single institution. Histologic type, tumor grade, invasion, pathologic stage, nodal status, metastasis, and the presence and type of variant morphology for each case were evaluated. Variant morphology was identified in 5 biopsy specimens (7.2%) and 42 resection specimens (13.4%). The most common variant morphologic pattern was squamous differentiation (16 cases, 4.5%) followed by an inverted growth pattern (8 cases, 2.2%). The presence of variant morphology in resection specimens had a significant association with higher tumor grade, higher pT stage, and non-papillary configuration. Out of 69 patients with biopsies, 31 had a subsequent resection. In comparison, 181 consultation cases from 168 patients showed variant morphology in six biopsies (7.1%) and twenty-seven resections (28.1%). In conclusion, the frequency of recognizing variant morphology in biopsies is about one-half of that in resections. The inclusion of consultation cases can inflate the incidence of variant morphology. As a result, the frequency of variant morphology in our in-house cases is lower than the percentage reported in the literature, most likely secondary to a consultation bias.

Human pathology. 2017 May 12 [Epub ahead of print]

Hiroyuki Hayashi, Steven Mann, Chia-Sui Kao, David Grignon, Muhammad T Idrees

Department of Pathology and Laboratory Medicine, Indiana University School of Medicine, Indianapolis, IN 46202., Department of Pathology, Stanford University Medical Center, Stanford, CA 94305., Department of Pathology and Laboratory Medicine, Indiana University School of Medicine, Indianapolis, IN 46202.. Electronic address: .