Background: Papillary renal neoplasm with reversed polarity is a rare entity, with its latest definition established only in 2019. Given its rarity, with less than 100 reported cases, further characterization is needed to enhance diagnostic accuracy and inform management strategies. Case Presentation: We report a case in a 64-year-old Chinese male with an incidentally discovered a size of 5.2cm× 4.0cm left renal mass on imaging. The patient has a medical history of coronary heart disease and left lower limb numbness. Further evaluation via contrast-enhanced CT confirmed that a nodular slightly hyperdense lesion approximately 52mm*39mm in size is noted in the left kidney. He underwent a partial nephrectomy and postoperative pathology confirmed PRNRP. Under the microscope, papillary structures can be seen lining a single layer of cuboidal epithelial cells in the left renal cyst and tumor. The nucleus appears low-grade, round, reverse nuclear polarity, and the nucleolus is not obvious. The tumor has not invaded the renal parenchyma. Immunohistochemistry confirmed P504S (+), CK7 (+), CK-H (+), GATA-3 (+), E-Cadherin (+), CK20 (Partial weak+), Vimentin (−), CD10 (individual+), CA-IX (−), RCC (−), Ki-67 (Li 1%). Postoperative recovery was excellent. The patient in this case did not receive any other treatment after surgery. Through regular telephone follow-up for 3 months, the patient’s condition was good. Ultrasound examination was performed during the period, and no recurrence or metastasis was found. Conclusion: This article presents a case of papillary renal neoplasm with reversed polarity in an elderly male patient. By reviewing the patient’s diagnosis and treatment process and revisiting relevant literature, the clinicopathological features of this tumor are elucidated to enhance understanding of this rare renal tumor. This case reinforces the distinct morphological and molecular profile of PRNRP, distinguishing it from other papillary RCC subtypes. The indolent behavior, absence of metastatic cases, and characteristic molecular profiling and immunohistochemical markers highlight the importance of accurate classification for optimal patient management. As PRNRP is recently classified, continued study is essential to refine diagnostic, therapeutic, and surveillance strategies for this rare renal neoplasm. Keywords: papillary renal neoplasm with reverse polarity, PRNRP, immunohistochemistry, rare case, renal tumors
Wang et al. (Mon,) studied this question.