Spatial Immune Profiling Reveals Distinct Microenvironments in Medullary Thyroid Carcinoma

Maria Eduarda De Castro¹Gustavo Forlin De Siqueira¹Jean Ferrante Mariano¹Marina Malta Letro Kizys¹Lucieli Ceolin¹Fernando Augusto Soares²Rodrigo Natal²Humberto Carneiro²Rodrigo Nalio Ramos^2,3Laura Sterian Ward⁴Niels Olsen Saraiva Camara³Cleber P. Camacho^1,5Flavia de Oliveira Facuri Valente¹Susan Chow Lindsey¹Diego Dias dos Santos⁶Cristiane Damas Gil⁶João Roberto Maciel Martins¹Rui Monteiro De Barros Maciel^1*Lucas Leite Cunha^1,7

• ¹Laboratory of Molecular and Translational Endocrinology, Department of medicine, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, Brazil
• ²Pathology Division, D'Or Research Institute, Rede D'Or Hospitals Network, São Paulo, Brazil
• ³Department of Immunology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Sao Paulo, Brazil
• ⁴Laboratory of Cancer Molecular Genetics, School of Medical Sciences, University of Campinas (UNICAMP), Campinas, Brazil
• ⁵Molecular Innovation and Biotechnology Laboratory, Postgraduate Medicine Program, Universidade Nove de Julho (UNINOVE), São Paulo, Brazil
• ⁶Department of Morphology and Genetics, Paulista School of Medicine, Federal University of Sao Paulo, São Paulo, São Paulo, Brazil
• ⁷Emergency Medicine and Evidence Based Medicine Unit, Department of Medicine, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, Brazil

Introduction: Medullary thyroid carcinoma (MTC) is a rare and aggressive thyroid cancer with a challenging prognosis. While the immune microenvironment plays a crucial role in cancer progression, its role in MTC remains underexplored compared to more common thyroid cancers. Methods: this study investigates the immune landscape of MTC by systematically evaluating immune cell infiltration and expression of immune markers across various tissue topographies. We utilized advanced immunohistochemical techniques to analyze tissue samples from 24 MTC patients, focusing on the tumor core, interface with healthy tissue, adjacent normal thyroid tissue, and lymph node metastases.Results: our findings reveal a distinct immune profile with increased CD3+, CD4+, CD8+ and CD20+ lymphocytes in normal tissues adjacent to tumors and a notable presence of granzyme B+ cells in the tumor interface, particularly in patients with structural disease. Additionally, we observed a significant enrichment of mast cells in metastatic tissues. Discussion: these results highlight the complex and spatially dependent immune landscape of MTC, suggesting implications for targeted immunotherapy.This study provides novel insights into the immune microenvironment of MTC and emphasizes the need for further research to elucidate its impact on disease progression and therapeutic response.