# Imaging Pitfalls of Multilocular Cystic Renal Neoplasm of Low Malignant Potential: A Case Report

## TL;DR

A rare kidney tumor was mistakenly seen as a solid mass on imaging, highlighting the difficulty in diagnosing it without surgery.

## Contribution

This case highlights the imaging challenges of diagnosing MCRNLMP as a solid tumor in elderly patients.

## Key findings

- MCRNLMP appeared solid on CT and MRI, mimicking a malignant tumor.
- Postoperative analysis confirmed the lesion was MCRNLMP with fibrous septa and intracystic hemorrhage.
- Fibrous tissue can create imaging appearances similar to solid tumors, leading to diagnostic confusion.

## Abstract

Multilocular cystic renal neoplasm of low malignant potential (MCRNLMP) is a rare subtype of renal tumor classified within the spectrum of clear cell renal tumors, and it is characterized by an excellent prognosis. Histologically, it is composed of multiple cysts lined by low-grade clear cells and separated by fibrous septa, with no solid expansile growth or significant nuclear atypia. Few reports have documented MCRNLMP mimicking a solid mass, especially in elderly patients. We report the case of an 80-year-old male in whom a left renal mass was incidentally detected during abdominal imaging performed as part of diabetes screening, and was ultimately diagnosed as MCRNLMP. Contrast-enhanced CT and MRI revealed a lesion in the mid-portion of the left kidney that appeared predominantly solid, raising strong suspicion for a malignant renal tumor. Robot-assisted nephrectomy (RAN) was performed, and postoperative histopathological analysis confirmed the diagnosis of MCRNLMP. The lesion showed prominent fibrous septa and intracystic hemorrhage, which likely contributed to its solid appearance on imaging. This report illustrates a diagnostic pitfall, where fibrous tissue may mimic solid tumor components on imaging, making it difficult to distinguish MCRNLMP from other solid renal tumors.