[826] Clear Cell Papillary Cystadenoma of the Epididymis and Mesosalpinx: Immunohistochemical Relationship to Clear Cell Papillary Renal Cell Carcinoma (RCC)

Roni Cox, Jonathan I Epstein. The Johns Hopkins Hospital, Baltimore, MD

Background: Clear cell papillary cystadenoma of the epididymis and mesosalpinx is rare and may be associated with von Hippel Lindau disease. Although rare, metastases of clear cell RCC to the testis and paratesticular region have been documented. Prior studies on a few cases showed the efficacy of CK7 and RCC in differentiating between this entity and metastatic clear cell renal cell carcinoma. Due to the emergence of additional markers commonly used in evaluating a renal origin for metastatic RCC, we have evaluated the immunohistochemical staining patterns of clear cell papillary cystadenomas using both CK7 and RCC as well as PAX 8, carbonic anhydrase IX (CAIX), and AMACR.
Design: Six cases of clear cell papillary cystadenoma were retrieved from our consult files from 2003-2011. 5 cases involved the epididymis and 1 involved the mesosalpinx. Patients ranged in age from 20-65 years.
Results: The lesions were composed of cysts, tubules, and papillary cores, lined by cuboidal to columnar bland-appearing cells with clear cytoplasm. In 3 cases there was reverse polarity of nuclei. All cases had areas that resembled the newly described clear cell papillary RCC. All lesions were strongly positive for CK7, yet AMACR staining was negative in 4 of the 6 cases; the remaining 2 cases showed only focal, weak staining. CAIX was positive in all lesions (diffusely positive in 5, patchy in 1), yet all were negative for RCC. PAX 8 showed diffuse positivity in 5 of the 6 lesions, with 1 epididymal lesion negative.
Conclusions: Clear cell papillary cystadenoma of the epididymis and mesosalpinx are morphologically similar to, and can be confused with, metastatic clear cell RCC. Due to the prevalence of both entities in patients affected by von Hippel Lindau diesease, and the propensity for clear cell RCC to metastasize to unusual sites, immunohistochemical markers are a useful adjunct in the diagnosis of the two lesions. Although a positive CK7/negative RCC staining profile can be used to differentiate clear cell papillary cystadenoma from metastatic clear cell RCC, care must be taken when using the newer markers for renal origin, as both carbonic anhydrase IX and PAX 8 are commonly positive in both lesions. An additional interesting finding is the similarity in the staining pattern of clear cell papillary cystadenoma to the recently described clear cell papillary RCC, along with the observation that they also share certain morphological features.
Category: Genitourinary (including renal tumors)

Monday, March 19, 2012 1:00 PM

Poster Session II # 133, Monday Afternoon


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