The Immune Microenvironment of Chordomas: An Immunohistochemical Analysis

SIMPLE SUMMARY: Chordoma patients may be amenable to immunotherapy; however, the immune microenvironment of chordomas needs further investigation. We performed the immunohistochemical analysis of a chordoma series, showing that these tumors have a unique microenvironment characterized by the absence of PD-L1 tumor cell expression, but feature PD-L1+ immune cells playing a negative prognostic role. ABSTRACT: Chordomas are rare sarcomas that are usually treated by surgery and/or radiotherapy since these are chemo-resistant tumors, but immunotherapy could be a possible option for chordoma patients. However, few reports investigating the composition of the chordoma immune microenvironment exist. We immunohistochemically studied 81 chordomas regarding their immune microenvironment factors and compared them with clinicopathological data. Macrophages and CD4 cells were the most prominent inflammatory cell populations, followed by CD8 T cells, while CD20 B cells and high endothelial venules (MECA-79+) were less frequently found. PD-L1 (22C3) expression by inflammatory cells was found in 21 (26%) tumors and was associated with a larger tumor size. None of the cases showed the expression of PD-L1 by tumor cells. Survival analysis showed that younger patients had a better overall survival. Considering the immunohistochemical factors studied, higher CD8, the presence of PD-L1+ immune cells, and higher vascular density were adverse prognostic factors, but in multivariate analysis, only PD-L1+ immune cells retained prognostic significance. To conclude, chordoma tumor cells do not express PD-L1, but PD-L1+ immune cells seem to play a negative prognostic role, supporting the need for further studies in this field and the possible beneficial role of immunotherapy in these patients.