Invasive low-grade papillary urothelial carcinoma: a clinicopathologic analysis of 41 cases.

Typically in invasive papillary urothelial carcinoma both the overlying papillary and the invasive components are high grade. We describe a series of patients with invasive low-grade papillary urothelial carcinoma (LPUC) in which both the noninvasive and invasive components are low grade. A retrospective search from The Johns Hopkins Surgical Pathology Database and consult cases from one of the author's files from 1998 to 2011 found 54 cases of invasive LPUC, excluding the more common, unique, and already well-characterized nested variant of urothelial carcinoma. Slides were available for 41 cases and formed the basis of the current study. The mean patient age was 68.4 years, with a male predominance. The specimens consisted of 37 bladder biopsies, 1 renal pelvis biopsy, 1 cystoprostatectomy specimen, 1 nephrectomy specimen, and 1 nephroureterectomy specimen. In all cases, invasion was limited to the superficial lamina propria above the muscularis mucosae. None of the histologic features correlated with tumor recurrence. Follow-up information was available for 73% of cases, with an average time interval of 49 months. Recurrent tumor was identified in 10/29 (34%) cases; however, 34% of cases without recurrence had limited follow-up (<24 mo). Three patients showed progression in tumor grade, and 3 additional patients progressed in both grade and stage (60% stage/grade progression). Four patients developed recurrence with ureteral noninvasive LPUC (2 in the bladder and 2 in the ureter). All are alive without disease. As this lesion is being increasingly recognized, larger studies are needed to determine whether invasion arising in LPUC is a significant risk factor for future disease.