Clinicopathological characteristics and typing of multilocular cystic renal neoplasm of low malignant potential

BACKGROUND Up until now,no research has been reported on the association between the cli-nical growth rate of multilocular cystic renal neoplasm of low malignant potential(MCRNLMP)and computed tomography(CT)imaging characteristics.Our study sought to examine the correlation between them,with the objective of distin-guishing unique features of MCRNLMP from renal cysts and exploring effective management strategies.AIM To investigate optimal management strategies of MCRNLMP.METHODS We retrospectively collected and analyzed data from 1520 patients,comprising 1444 with renal cysts and 76 with MCRNLMP,who underwent renal cyst decom-pression,radical nephrectomy,or nephron-sparing surgery for renal cystic disease between January 2013 and December 2021 at our institution.Detection of MC-RNLMP utilized the Bosniak classification for imaging and the 2016 World Health Organization criteria for clinical pathology.RESULTS Our meticulous exploration has revealed compelling findings on the occurrence of MCRNLMP.Precisely,it comprises 1.48%of all cases involving simple renal cysts,5.26%of those with complex renal cysts,and a noteworthy 12.11%of renal tumors coexisting with renal cysts,indicating a statistically significant difference(P=0.001).Moreover,MCRNLMP constituted a significant 22.37%of the patient po-pulation whose cysts demonstrated a rapid growth rate of≥2.0 cm/year,whereas it only represented 0.66%among those with a growth rate below 2.0 cm/year.Of the 76 MCRNLMP cases studied,none of the nine patients who underwent subsequent nephron-sparing surgery or radical nephrectomy following renal cyst decompression experienced recurrence or metastasis.In the remaining 67 patients,who were actively monitored over a 3-year postoperative period,only one showed suspicious recurrence on CT scans.CONCLUSION MCRNLMP can be tentatively identified and categorized into three types based on CT scanning and growth rate indicators.In treating MCRNLMP,partial nephrectomy is preferred,while radical nephrectomy should be minimi-zed.After surgery,active monitoring is advisable to prevent unnecessary nephrectomy.

The pathology of urinary bladder lesions with an inverted growth pattern

Inverted lesions in the urinary bladder have been the source of some difficulty in urological pathology. The two common ones are von Brunn＇s nests and cystitis cystic/cystitis glandularis, which are considered normal variants of urothelium. Apart from them, a number of other rare urothelial lesions with inverted growth pattern occur in the urinary bladder. Some of them are only reactive conditions, just as pseudocarcinomatous hyperplasia. Some are benign tumors, namely inverted papilloma. Whereas others are malignant neoplasms, including inverted papillary urothelial neoplasm of low malignant potential （PUNLMP）, non-invasive inverted papillary urothelial carcinoma （low-grade and high-grade）, and invasive urothelial carcinoma （inverted, nested and big nested variants）. Because of the overlapping morphological features of all the inverted lesions mentioned above, even between high-grade invasive carcinoma and psendoearcinomatous hyperplasia which are only a kind of reactive conditions, it is very important for the surgical pathologist to recognize and be familiar with these inverted lesions in urinary bladder. In this article, we review these spectrums of inverted lesions of the urinary bladder. Emphasis is placed on histogenesis, morphology, differential diagnosis of these lesions, and the pathologic grading of the non-invasive inverted neoplasms, such as inverted papilloma, inverted PUNLMP, non-invasive inverted papillary urothelial carcinoma with low-grade, and non-invasive inverted papillary urothelial carcinoma with high-grade.