# Oncocytic Hyperplastic Nodule Versus Oncocytic Adenoma: Diagnostic Controversies Through a Brief Investigative Case Series Study

## TL;DR

This study highlights the diagnostic challenges in distinguishing between oncocytic hyperplastic nodules and oncocytic adenomas in thyroid tissue.

## Contribution

The study presents cases with molecular findings that challenge current histological criteria for oncocytic adenomas.

## Key findings

- Two solitary oncocytic lesions showed pathogenic mutations in p53 and NRAS genes.
- Oncocytic nodules in autoimmune thyroiditis cases had no significant molecular findings.
- The study suggests reevaluating histological criteria for oncocytic adenomas to resolve diagnostic controversies.

## Abstract

Oncocytes are frequently encountered in routine thyroidectomies. The distinction between oncocytic hyperplastic nodules and oncocytic adenomas (OAs) may be challenging. Although both entities are benign, a precise diagnosis is essential. We present two cases of solitary oncocytic lesions carrying pathogenic mutations in the p53 and NRAS genes, respectively, leading to a histological diagnosis of oncocytic hyperplastic nodules. Additionally, similar oncocytic nodules from two cases of autoimmune thyroiditis did not show any significant findings on molecular analysis (next-generation sequencing, NGS). Hence, this brief investigative series study is of particular diagnostic interest because it prompts pathologists to use the term adenoma when a solitary oncocytic nodule is encountered, regardless of the established criteria for the diagnosis of adenoma. This viewpoint leads to the possible need for the reevaluation of the histological criteria of adenomas when it comes to oncocytic lesions in order to gain a common diagnostic approach and nomenclature among pathologists and overcome any controversies in such cases.