Heterogeneous Immune Landscapes and Macrophage Dynamics in Primary and Lung Metastatic Adenoid Cystic Carcinoma of the Head and Neck

Recurrent or metastatic adenoid cystic carcinoma (ACC) of the head and neck is rare and highly aggressive. Due to the ineffectiveness of immune checkpoint therapies, this study aims to investigate the tumor immune microenvironment of primary tumor tissues and lung metastatic tissues and to comprehend the challenges of immunotherapy. We analyzed RNA sequencing data and constructed immune landscapes from 25 primary tumors and 34 lung metastases. Compared to adjacent normal tissues, both primary and lung metastatic ACC showed low immune infiltration. Lung metastases had higher immune infiltration levels and antigen presentation scores but also higher T cell exclusion and dysfunction scores. Higher immune cell infiltration in lung metastases is countered by the presence of suppressive tumor-associated macrophages, which may limit effective anti-tumor responses.