# Prognostic factor analysis of oral and maxillofacial Langerhans cell histiocytosis based on clinical findings and tumour microenvironment

## TL;DR

This study explores the prognosis of oral and maxillofacial Langerhans cell histiocytosis by analyzing clinical factors and immune cell dynamics.

## Contribution

The study introduces new insights into the role of Treg cells and M2 macrophages in LCH-OMF prognosis.

## Key findings

- No patient with CNS risk region lesions developed CNS-related disease.
- One patient with multi-system LCH had the poorest prognosis, possibly due to increased Tregs causing immunosuppression.
- M2 macrophage IL-10 secretion may initiate tumor growth, though this is hypothesis-generating.

## Abstract

This study aimed to investigate the clinical prognostic factors of oral and maxillofacial Langerhans cell histiocytosis (LCH-OMF) and the dynamics of regulatory T (Treg) cells and M2 macrophages.

We retrospectively analysed nine patients who were definitively diagnosed with LCH-OMF and examined clinical factors including age, sex, disease type, lesion site, clinical findings, the presence or absence of central nervous system (CNS) risk lesions, other organ lesions, treatment methods and prognosis. Immunohistochemical and fluorescent immunohistochemical analyses were performed to investigate prognostic factors from a cell biological perspective regarding the mechanism of onset in these patients.

None of the nine patients followed the previously reported clinical prognostic patterns, and no patient with lesions in cranio-maxillofacial bones within the CNS risk region developed CNS-related disease. One patient had multi-system LCH with risk organ involvement (MS [RO +]) and the poorest prognosis; in this case, an increase in Tregs in the LCH lesion may have caused tumour immunosuppression, suggesting an association with disease severity. Findings from this patient suggested that interleukin (IL)-10 secretion by M2 macrophages may be an initiating factor in the mechanisms that regulate tumour growth; however, this interpretation is hypothesis-generating and based on a small number of cases.

Assessing the prognosis of LCH-OMF requires a comprehensive consideration of the disease type, age, CNS-risk regions, risk organs, acute systemic inflammatory response, and skin involvement. A better understanding of IL-10 derived from Tregs and M2 macrophages in LCH-OMF and in LCH overall may enhance our comprehension of inflammatory dysregulation and Langerhans cell progression in LCH and could help to identify potential treatment strategies.