[850] Immunohistochemical Profile of Clear Cell and Related Renal Cell Cancers, with Emphasis on CK7 and Carbonic Anhydrase-IX (CA-IX) Staining

Samson W Fine, Ying-Bei Chen, Hikmat A Al-Ahmadie, Anuradha Gopalan, Victor E Reuter, Satish K Tickoo. Memorial Sloan-Kettering Cancer Center, New York, NY

Background: Immunohistochemical (IHC) staining is often used as an important differential diagnostic adjunct for renal tumors, both in metastatic and primary settings. In this differential, clear cell renal cell carcinoma (CC-RCC) is usually considered as CA-IX and CD10 diffusely positive and CK7 negative. We have occasionally observed unusual staining patterns among typical CC-RCCs mimicking those in other RCCs that may be considered in their differential diagnosis. Using a small panel of commonly used stains, we analyzed the IHC patterns in CC- RCC and some of its closely related entities.
Design: IHC was performed for CK7, CA-IX, CD10, and 34BE12 on 10 cases of clear cell papillary RCC (CCP), 7 multilocular cystic RCC (MLC), 7 clear cell RCC with prominent (>35%) cystic component (CC-RCC-C), and 15 clear cell RCCs without cystic change (CC-RCC-NC). Immunoreactivity was analyzed for percent cells positive, location of positive staining, and patterns of staining.
Results: CK7 positivity was present in all cases of CCP, MLC and CC-RCC-C, with 100% cells staining positive in 10/10 CCP and 2/7 MLC. 2 (13%) CC-RCC-NC showed very focal CK7 reactivity, but only in small cystic areas present in these 2. CK7 positivity was also more concentrated in and around cystic areas in CC-RCC-C. CA-IX was positive in all cases in all 4 tumor groups, but only CCP showed a predominantly “cup-like” reactivity with absence of staining on luminal aspect of the cells. CD10 was either completely negative, or was only very focally positive in CCP (2/7, 20% cases) and MLC (3/7, 43%), mostly in a luminal pattern. Whereas, CD10 positivity was seen in 71% of CC-RCC-C (mixed luminal and box patterns) and 87% of CC-RCC-NC (predominantly box-pattern), respectively. 34BE12 was mainly positive in CCP and MLC (60 and 43% cases), with only 1 case each of CC-RCC-C and CC-RCC-NC showing focal reactivity.
Conclusions: 1) CK7 immunoreactivity should not exclude the possible diagnosis of clear cell RCC, particularly in cystic lesions; however, diffuse positive staining in 100% or close to 100% cells in a tumor is not a characteristic of clear cell RCC.
2) CK7 positivity appears to be mostly related to cystic features in the tumors, except in clear cell papillary RCC, where it stains all the cells irrespective of relationship to cystic areas.
3) Diffuse membranous CA-IX reactivity is seen in a variety of clear cell tumors, but “cup-shaped” reactivity is a characteristic of only clear cell papillary RCC.
Category: Genitourinary (including renal tumors)

Tuesday, March 20, 2012 9:30 AM

Poster Session III # 153, Tuesday Morning


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