[908] Her2 Expression in Urothelial Carcinoma with Micropapillary Morphology: Preferential Overexpresssion by the Micropapillary Component

Hongying Huang, Sana Jadallah, Ying-Bei Chen, Anuradha Gopalan, Samson W Fine, Satish K Tickoo, Gopakumar V Iyer, Guido Dalbagni, David Solit, Victor E Reuter, Hikmat A Al-Ahmadie. Memorial Sloan-Kettering Cancer Center, New York, NY

Background: Micropapillary carcinoma (MPC) of the bladder is a rare but reportedly highly aggressive variant of urothelial carcinoma (UC). Histologically, most of these tumors are usually associated with variable amounts of classical UC. It has been recently reported that MPC is more likely to be associated with amplification of the human epidermal growth factor receptor-2 (ERBB2; Her2), but Her2 status in the classical UC component in these mixed tumors has not been addressed. We sought to evaluate the intratumoral heterogeneity regarding Her2 by comparing its expression in MPC and classical UC components within the same tumor by immunohistochemistry (IHC).
Design: We identified 37 cases of primary bladder UC containing both MPC and classical UC areas. IHC was performed for Her2 on representative paraffin blocks containing both the components. Her2 expression was assessed using the American Society of Clinical Oncology/College of American Pathologists Guidelines set for mammary carcinoma; Her2 was considered to be overexpressed when the IHC score was 2+ or 3+.
Results: Overall, 21 cases (58%) demonstrated Her2 protein overexpression in the MPC component, including 11 cases with 3+ staining and 10 cases with 2+ staining. In contrast, 5 cases (14%) demonstrated Her2 protein expression in the conventional component, including 2 cases with 3+ staining and 3 cases with 2+ staining. Of the 21 cases with Her2 overexpression in the MPC component, 3 cases (14%) showed similar expression (2+ to 3+) in the classical component, whereas the other 18 cases (86%) were negative for Her2 expression (score 0 to 1+) in the conventional component.
Conclusions: The majority of micropapillary carcinomas of the bladder overexpress Her2. Her2 is preferentially overexpressed in micropapillary component compared to the classical UC component within the same tumor in the majority of cases. These findings support the presence of intratumoral heterogeneity of Her2 overexpression in UCs containing MPC component.
Category: Genitourinary (including renal tumors)

Tuesday, March 5, 2013 9:30 AM

Poster Session III # 99, Tuesday Morning


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