RESUMO
BACKGROUND: Differentiation between normal renal cellular structures and renal tumors can be a diagnostic challenge during fine needle aspiration. It is of particular relevance during percutaneous thermal ablation because of the small size of tumors and when performing rapid on-site evaluation. METHODS: A cyto-histological correlation study assisted by immunocytochemistry was performed. The study was based on 10 nephrectomy specimens. For the identification of proximal tubular cells we used CD10 and α-methylacyl coenzyme A racemase (AMACR). PAX8 and GATA3 were used for the recognition of distal and collecting duct cells. For a precise correlation representative cytologic groups were photographed before and after immunocytochemistry. RESULTS: All cases showed: (a) glomeruli; (b) presence of at least 2 different epithelial cell populations that distribute separately, one representing the proximal tubule and the other more distal segments; and (c) existence of isolated, laminar basement fragments and slender, intact tubular structures. Proximal tubular cells were large with granular cytoplasm, indistinct cell borders, moderate anisonucleosis, and variable presence of pigment. Their immunophenotype was CD10+, AMACR+, PAX8-, and GATA3-. In all cases, cellular aggregates different of nonproximal tubular cells were present. They were smaller than proximal tubular cells with less cytoplasm, better-defined cell borders and uniform nuclei. Their immunophenotype was CD10-, AMACR-, PAX8+, and GATA3+ CONCLUSION: Aspirates from the normal kidney show characteristic features that permit a specific recognition. Different segments of the tubular system can be specifically recognized avoiding confusion with renal tumors. In difficult cases immunocytochemistry is a very helpful aid.