[1051] Clinicopathologic and Immunohistochemical Characteristics of Invasive Low Grade Urothelial Carcinoma

Katherine E Watts, Donna E Hansel. Cleveland Clinic, Cleveland, OH

Background: Papillary urothelial carcinomas (UC) are broadly categorized into low and high-grade categories, with the former generally occurring as non-invasive lesions and the latter with or without invasion. Low-grade papillary UC may rarely be associated with invasion, although the properties that distinguish these lesions from the less aggressive, more prototypical papillary low-grade UCs is unclear. We therefore examined the clinicopathologic and immunohistochemical features associated with the uncommon subset of invasive low-grade papillary UC.
Design: The electronic archives were searched for cases of invasive low grade papillary UC between 2001 and 2008 and the appropriate slides reviewed. Clinical and outcomes data were extracted from the electronic medical record. Immunohistochemical stains for p53, CK20, E-cadherin, and CD44 were performed on routine formalin-fixed paraffin-embedded sections.
Results: Twelve cases of invasive low-grade papillary UC were identified. All but one of the patients were male (mean age 64 yrs; range 37-82 yrs). Five patients had a subsequent non-invasive low-grade papillary UC, with recurrence at an average of 9.6 months after initial diagnosis, 1 had a subsequent high-grade invasive UC on radical cystectomy, and 4 had no evidence of recurrence. One patient was found to have metastatic disease at the time of diagnosis and a second developed metastatic disease within 17 months; both of these patients died of their disease. Two cases showed invasion of the muscularis propria (MP) and 10 showed superficial invasion of the lamina propria. All cases showed diffuse expression of nuclear p53 and maintained E-cadherin expression throughout the lesion. Immunostaining for CK20 was more variable, with 5 cases showing strong diffuse staining throughout the papillary component (including 1 case with MP invasion) and 6 cases showing focal non-umbrella cell staining. CD44 was weakly present in a basilar distribution in 3 cases, whereas 3 other cases showed focal strong non-basilar expression, and 6 showed focal weak non-basilar staining; complete absence of CD44 staining was not seen in any case.
Conclusions: Immunohistochemical stains for p53 in cases of invasive low-grade papillary UC showed a similar pattern of expression to that associated with invasive high-grade papillary UC, suggesting its possible utility in predicting low-grade papillary UC cases that are likely to display more aggressive biological behavior. Further investigation into the differences of E-cadherin, CK20 and CD44 staining patterns in this unusual subset of cases is warranted.
Category: Genitourinary (including renal tumors)

Tuesday, March 20, 2012 1:00 PM

Poster Session IV # 95, Tuesday Afternoon


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