Renal tumors account for about 3% of the malignancies in adults. Clear cell subtype renal cell carcinoma (RCC) and papillary RCC are the most common renal tubular epithelial carcinomas and their differentiation is important because they have a different prognosis and are associated with different treatment protocols. In most cases, histological features allow accurate diagnosis of renal cell carcinomas. There are also overlapping morphological findings between certain kidney neoplasms that make their subtyping extremely difficult. Some of them display papillary architecture but also have a clear cell component and it is not clear whether they should be classified as clear cell RCC or papillary RCC.
In our study we performed an immunohistochemical and genetic analysis of 24 cases of RCC classified as non-classifiable with mixed papillary and clear cell components treated at Clinic of Urology in University Hospital "St. George "-Plovdiv. The mean age of patients was 54.5 years, and gender distribution: 60% male and 40% female.
Based on the results of immunohistochemistry and fluorescence in situ hybridization (FISH), patients were stratified in 2 groups. The first group included 16 of the cases where strong immunoreactivity was found for alfa-methyl coenzyme A racemase (AMACR), with cytokeratin 7 (CK7) being present in 15 of these. In all cases in this group, FISH proved trisomy 7 and 17, in 4-9p deletion, and in 2- 3p deletion. The remaining 8 cases were stratified in the second group - all negative for CK7 and only one positive for AMACR. Genetic analysis showed a lack of trisomy 7 and 17 in all cases, as well as a deletion of 3p and 9p in 7 of them.
The combination of immunohistochemical and genetic analyzes allows with a high accuracy to differentiate cases of papillary RCC from those with clear cell RCC.
Preservation of truncal genomic alterations in clear cell and papillary renal cell carcinomas with sarcomatoid features: An intra- and intertumoral, multifocal fluorescence in situ hybridization analysis reveals limited genetic heterogeneity
