# Multilocular cystic nephroma in a 15-month-old infant: Successful surgical management and 10-year follow-up

## TL;DR

A 15-month-old infant with a kidney tumor was successfully treated with surgery and remained healthy for 10 years, showing that this rare tumor is benign but hard to diagnose before surgery.

## Contribution

This case highlights the importance of surgical excision for both diagnosing and treating MLCN, and confirms its benign nature with excellent long-term outcomes.

## Key findings

- MLCN can closely resemble malignant tumors on imaging, leading to diagnostic challenges.
- Surgical excision is both diagnostic and curative for MLCN with no recurrence after 10 years.
- A multidisciplinary approach is essential for managing pediatric cystic renal masses.

## Abstract

Multilocular cystic nephroma (MLCN) is a rare benign renal tumor of uncertain etiology that affects primarily infants and young children. Clinically and radiologically, it can closely resemble malignant renal tumors such as cystic partially differentiated nephroblastoma (CPDN) and cystic Wilms tumors, which makes a precise preoperative diagnosis particularly challenging.

We report the case of a 15-month-old male infant who presented nonspecific symptoms, including diarrhea, reduced appetite, and progressive abdominal distension. Physical examination revealed a failure to thrive and a well-defined and firm abdominal mass. Imaging studies demonstrated a multilocular cystic lesion in the left kidney without evidence of calcification, lymphadenopathy, or metastasis. Due to diagnostic ambiguity and the suspicion of malignancy, an open radical nephroureterectomy was performed. Gross pathology revealed a multiloculated mass filled with clear fluid, and histological evaluation confirmed the diagnosis of MLCN.

This case underscores the difficulty in distinguishing MLCN from malignant cystic renal tumors based solely on imaging. Although MLCN is benign, the potential for misdiagnosis requires surgical intervention. Complete excision remains both diagnostic and curative. Long-term outcomes are excellent, with a low risk of recurrence or malignant transformation. In our case, the child recovered well after the operation and showed no evidence of recurrence after ten years of follow-up, highlighting the favorable prognosis with appropriate treatment.

MLCN should be considered in the differential diagnosis of pediatric cystic renal masses. Despite its benign behavior, surgical resection is often required due to diagnostic uncertainty. This case illustrates the importance of a multidisciplinary approach in the evaluation of renal tumors in children and reinforces the need for long-term follow-up.

•Multilocular cystic nephroma (MLCN) is a rare benign renal tumor in infants that often mimics malignant cystic renal lesions radiologically, making preoperative diagnosis difficult.•Definitive diagnosis of MLCN relies on histopathological examination following surgical excision, which also serves as curative treatment.•This case demonstrates the excellent long-term outcome of MLCN post-nephrectomy, with no recurrence observed over a 10-year follow-up period.

Multilocular cystic nephroma (MLCN) is a rare benign renal tumor in infants that often mimics malignant cystic renal lesions radiologically, making preoperative diagnosis difficult.

Definitive diagnosis of MLCN relies on histopathological examination following surgical excision, which also serves as curative treatment.

This case demonstrates the excellent long-term outcome of MLCN post-nephrectomy, with no recurrence observed over a 10-year follow-up period.