# Oncocytic Features in Choroid Plexus Tumors: An Integrative Clinicopathological Study

## TL;DR

This study explores oncocytic features in choroid plexus tumors and links them to inflammation, hypoxia, and immune responses.

## Contribution

The study identifies oncocytic changes in CPTs and their association with immune markers and ciliary dysfunction for the first time.

## Key findings

- Oncocytic changes were observed in 36% of CPP cases and linked to mortality, necrosis, and hemorrhage.
- Oncocytic features showed positive reactions to immune-related markers like IL-2, IL-6, and TNF-α.
- The study suggests oncocytic changes may involve dendritic cells and ciliary dysfunction in CPTs.

## Abstract

Background: Choroid plexus tumors (CPTs) are rare epithelial brain tumors. Recent studies have found changes in the cells and the presence of amyloid, but these tiny details are still not well understood. Limited information is available regarding the biology of oncocytic changes (OCs) in CPTs.

Material and methods: This study included 42 primary and recurrent CPTs. Out of these, 28 cases (67%) were grade I choroid plexus papilloma (CPP), eight cases (19%) were grade II atypical choroid plexus papilloma (ACPP), and six cases (14%) were grade III choroid plexus carcinomas (CPCs), based on the World Health Organization (WHO) 2021 classification.

Results: We observed OCs in 10 (36%) CPP cases, three (38%) ACPP cases, and one (17%) CPC case (p = 0.643). We correlated these changes with mortality (p = 0.049), necrosis (p = 0.014), hemorrhage (p = 0.000), amyloid deposition, psammoma bodies, and brain invasion. OCs showed a positive reaction to fascin, CD1a, interleukin (IL)-2, IL-6, tumor necrosis factor-alpha (TNF-α), CD68, and hypoxia-inducible factor 1-alpha (HIF-1α), but the epithelial cells in CPP and CPC did not react. The detailed examination showed both normal and unusual mitochondria, fat droplets, thread-like materials, microtubules, amyloid buildup, and problems with cilia.

Conclusion: OCs in CPTs are rare and likely associated with inflammatory, ischemic, and hypoxic conditions. These changes might show dendritic cells (DCs) that help protect the blood-brain barrier, monitor the immune system, or support aging cells that promote flexibility and healing in tissues. Furthermore, we linked them to ciliary dysfunction. We need further studies to better understand this rare phenomenon in CPTs.