Low Grade Urothelial Carcinoma with Focal High Grade Component of the Urinary Bladder: Pathological Outcomes in Follow-Up Biopsies
Yi Ding, Oksana Yaskiv, Theresa Chan, Fang-Ming Deng, Jonathan Melamed, Ming Zhou. New York University Langone Medical Center, New York, NY; North Shore Long Island Jewish Health System, Lake Success, NY
Background: Grade heterogeneity is well recognized in urothelial carcinoma (UC). Empirically, any tumor with >5% high grade (HG) component is diagnosed as high grade UC (HGUC), while a low grade UC (LGUC) with <5% HG component is diagnosed as LGUC with focal HG component. However, it is unclear how these tumors may behave. This study describes the histological features of LGUC with focal HG component and correlates them with pathological outcomes in follow-up biopsies.
Design: Bladder UC cases with “LG” and “HG” were retrieved (1999-2012) and the diagnosis of “predominant LG with <5% HG component” was confirmed. The clinical and histologic features were recorded, including age, gender, distribution of high grade cells (focal clustered vs diffuse scattered), nature of nuclear atypia (frank vs degenerative), mitosis and apoptosis, and tumor necrosis in both LG and HG components. Results of follow-up biopsies were recorded.
Results: 32 patients were identified as having “LGUC with focal HG component”. They had a mean age of 70.5 years (range 50-90), 24 males and 8 females. Morphological features are shown in the Table. During follow-up, benign or LGUC was found in 22 (68.8%) and HGUC in 10 (31.2%) patients. Patients with benign or LGUC on follow-up were significantly younger than those with HGUC. No morphological features are associated with HGUC on follow-up biopsies. Patients with focal clustered distribution and degenerative nuclear atypia tended to have benign or LGUC on follow-up.
|Follow-up results (n=32)||Benign or LGUC (n=22; 68.8%)||HGUC (n=10; 31.2%)||P value|
|Distribution of atypical cells||Focal clustered (n=26)||19 (73.1%)||7 (26.9%)||0.204|
|Diffuse scattered (n=6)||3 (50.0%)||3 (50.0%)|
|Nuclear atypia||Frank atypia (n=23)||14 (60.9%)||9 (39.1%)||0.114|
|Degenerative (n=9)||8 (88.9%)||1 (11.1%)|
|Mitosis in HG component (/HPF)||1.7 (range 0-9)||2.4 (range 0-10)||0.467|
|Mitosis in LG component (/HPF)||0.7 (range 0-5)||0.5 (range 0-5)||0.165|
|Apoptosis||4 (18.2%)||4 (40%)||NA|
|Tumor necrosis||2 (9.1%)||1 (10%)||NA|