Can We Identify Nephrogenic Adenoma in Urine Cytology Specimens? A Study Evaluating Previously Described Cytomorphologic Features in Correlation With PAX8 Immunohistochemical Staining Results.

Objectives: The aim of this study is to determine if the diagnosis of nephrogenic adenoma (NA) can be made on cytologic criteria alone and if pair box gene transcription factor 8 (PAX8) is useful in the diagnosis of NA in daily cytology practice.
Methods: Cytologic features of NA previously described in a literature were used to identify NA cells in urinary specimens. Subsequently, all cytology and corresponding biopsy specimens were stained with the PAX8 immunohistochemistry stain. The stains were examined; the results were tabulated.
Results: A total of 44 specimens were reviewed (35 with corresponding biopsy specimens diagnosed as NA and nine negative for NA diagnosis on corresponding biopsy specimens). Of them, 14 demonstrated features previously described as NA. None of atypical cells that were morphologically suspicious for NA showed positive staining, whereas all of the corresponding biopsy sections demonstrated nuclear PAX8 positivity. Only rare lymphocytes present in cytology specimens showed nuclear staining with PAX8.
Conclusions: Assuming that the results of the PAX8 stain performed are accurate at least in most cases, as suggested by the presence of internal positive controls, our study shows that the previously described cytologic features of NA cannot be used as diagnostic criteria, since they are not characteristic for this entity.
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