10-year Observation of A Rare Presentation of Pure Fibromyxoid Nephrogenic Adenoma in the Renal Pelvis

Abstract

Abstract Introduction/Objective Pure fibromyxoid NA is an unusual rare variant that typically presents with a well circumscribed bulbous, or tumefacient architecture composed of mitotically inactive bland spindled cells and rare tubular structures within a myxoid or collagenized stroma. Here we report a rare case of pure fibromyxoid NA involving the renal pelvis with over 10-year clinical observation and comparison and correlation of biopsy and resection findings. To the best of our knowledge, this is the first reported case of pure fibromyxoid NA in renal pelvis with close comparison and correlation of biopsy and resection findings with over 10-year clinical manifestation, hoping that knowledge of this long-term rare spindle cell lesion will enhance awareness of pathologists to carefully consider this unusual entity, especially in the biopsy specimen in which typical histologic features of fibromyxoid NA are usually absent, as well as prevent misdiagnosis and overtreatment of a typically benign process. Methods/Case Report A retrospective case study of a 37-year-old female with multiple previous biopsy of the nodule in the renal pelvis, and final resection specimen. Biopsies of the mass showed predominantly bland spindle cell lesion with smooth muscle differentiation and scant urothelial epithelial cells, but no tubular structure identified at the biopsy specimen. On the final resection specimen, a urothelium-lining polypoid nodule composing of abundant bland spindle- shaped cells and scattered conventional tubules lined by a single layer of cuboidal epithelial cells in hobnail arrangement that are positive for PAX8 and GATA3 was identified. These morphological and immunohistochemical findings were consistent with the diagnosis of pure fibromyxoid NA. Results (if a Case Study enter NA) NA Conclusion To the best of our knowledge, this is the first description of a pure fibromyxoid NA of the renal pelvis with more than 10-year clinical observation, as well as comparison and correlation of biopsy and resection findings.Close observation and comparison of the findinigs between biopsy and resection specimen will enhance awareness of pathologists to carefully consider this unusual entity, especially in the biopsy specimen in which typical histologic features of fibromyxoid NA are usually absent, as well as prevent misdiagnosis and overtreatment of a typically benign process.