[904] Divergent Morphology in Renal Pelvic Urothelial Carcinoma May Be Less Frequent Than Previously Reported

Chia-Sui Kao, Muhammed Idrees. Indiana University, Indianapolis, IN

Background: Renal pelvic urothelial carcinomas exhibiting aberrant morphology, especially in higher grade tumors, is a well recognized phenomenon, and divergent morphology had been reported to be as high as 40% in the literature. However, we feel that the frequency of divergent morphology is far less than the percentage previously reported and may be secondary to practice bias. Our goal is to study the occurrence of divergent morphology within renal pelvic urothelial carcinomas in our patient population excluding consultation cases and report the most common variants.
Design: From our surgical pathology files, 119 cases of primary renal pelvic urothelial carcinomas from nephro-uretercomy specimens within the past 10 years were identified and confirmed by reviewing hematoxylin and eosin stained sections. Histologic type, grade, invasion, stage, nodal status, metastasis, and the presence of divergent morphology were evaluated for all tumors. All the consultation cases where the surgery was performed elsewhere were excluded from the study.
Results: A total of 15 renal pelvic urothelial carcinomas out of a total of 119 cases show areas of divergent morphology, including squamous (27%), glandular/tubular (13%), sarcomatoid (13%), inverted (13%), mucinous (7%), plasmacytoid (7%), micropapillary (7%), lymphoepithelialoma-like (7%), and giant-cell (7%) differentiation. Two-thirds of the cases with divergent morphology occurred in high grade flat-type urothelial carcinomas, while the remaining one-third occurred in high grade papillary urothelial carcinomas. Divergent morphology was not observed in any of the low grade papillary urothelial carcinomas nor was it observed in the majority of high grade urothelial carcinomas of the renal pelvis.
Conclusions: Our study shows that divergent morphology occurs in only 13% of renal pelvic urothelial carcinomas in our hospital based patient population, instead of the higher percentage that had been previously reported in the literature. The ones with divergent morphology are mostly high grade invasive urothelial carcinomas; however, the majority of the high grade renal pelvic urothelial carcinomas do not actually show aberrant differentiation. The most frequently observed ones are squamous, glandular/tubular, sarcomatoid, and inverted patterns. We recognize that the lower frequency than that reported in the literature may be secondary to the type of practice and possibly overrepresented in the literature.
Category: Genitourinary (including renal tumors)

Wednesday, March 21, 2012 1:00 PM

Poster Session VI # 151, Wednesday Afternoon


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