Clinical observation of a patient with a papillary tumor of the kidney with reversed nuclear polarity

Papillary renal tumor with reverse nuclear polarity is a rare neoplasm with a favorable prognosis, recently identified separately in the classification of tumors of the urinary tract (2022). Previously, this tumor was considered a subtype of papillary renal cell carcinoma. However, papillary renal tumor with reverse nuclear polarity demonstrates unique morphological, immunohistochemical and genetic features, including frequent KRAS mutations and the absence of chromosomal abnormalities characteristic of papillary renal cell carcinoma. The main diagnostic difficulties are related to histopathological similarities with aggressive renal tumors (eg, papillary renal cell carcinoma) and variability in the expression of some markers. Errors in verification may lead to overtherapy, while papillary renal tumor with reverse nuclear polarity requires a less aggressive approach. The paper presents a clinical observation of a 65-year-old female patient with a papillary tumor of the kidney with reverse nuclear polarity. This case is of interest due to the rarity of this pathology and the complexity of its diagnosis.