# Primary Renal Neuroendocrine Tumor: Diagnostic Challenges in a Rare Entity—A Case Report

## TL;DR

This case report describes a rare primary kidney tumor that is difficult to diagnose due to its similarity to other kidney cancers and highlights its unique genetic features.

## Contribution

The paper presents a new case of PRNET and emphasizes its distinct genomic profile compared to common kidney cancers and NENs.

## Key findings

- PRNETs are exceptionally rare and challenging to diagnose due to non-specific symptoms and resemblance to other kidney tumors.
- The case highlights the genomic heterogeneity of PRNETs, which lack typical gene alterations seen in common kidney cancers or NENs.

## Abstract

Neuroendocrine neoplasms (NENs) are rare and heterogeneous tumors. Primary renal neuroendocrine tumors (PRNETs) are exceptionally uncommon, with approximately 160 cases reported worldwide. Since PRNETs present with non-specific clinical symptoms and closely mimic more common renal neoplasms, diagnosis is challenging and relies on specialized pathological evaluation. Here, we report the case of a 61-year-old woman with an incidentally discovered left-sided PRNET, illustrating the diagnostic challenges and underscoring the genomic heterogeneity of these tumors.

Neuroendocrine neoplasms (NENs) represent a rare, heterogeneous group of malignancies. Within this tumor entity, primary renal neuroendocrine tumors (PRNETs) are exceedingly rare, with only 160 cases reported worldwide. Due to the absence of native neuroendocrine cells in the renal parenchyma, their cellular origin remains unclear. Clinical and diagnostic challenges are reflected by the low incidence, non-specific clinical presentation, resemblance to common renal neoplasms, and the need for specialized histopathological diagnostic examination. Here, we present the case of a 61-year-old female with an incidentally diagnosed left-sided PRNET in September 2024. This case highlights the diagnostic complexity of PRNET and, importantly, underscores its genomic heterogeneity. It demonstrates a lack of typical renal cell carcinoma (RCC) or common NEN-associated gene alterations, emphasizing their unique molecular landscape.