CD20+ tumor‐infiltrating immune cells and CD204+ M2 macrophages are associated with prognosis in thymic carcinoma

CD20+ tumor‐infiltrating immune cells and CD204+ M2 macrophages are associated with prognosis in thymic carcinoma:

Abstract

Thymic carcinoma is a rare malignant disease with no standard systemic chemotherapy. The purpose of the present study was to investigate tumor‐infiltrating immune cells (TIICs) in the tumor microenvironment (TME), mainly the impact of TIICs and PD‐L1 expression on clinical outcomes in thymic cancer.

Patients with thymic carcinoma resected between 1973 and 2017 were investigated. The tissue specimens were analyzed through immunohistochemical staining to elucidate the prognostic effects of TIICs, their ratios, and PD‐L1 in a preliminary cohort (n=10). The density of TIICs as well as PD‐L1 expression was evaluated in intraepithelial and tumor‐stromal areas on the representative whole section of tumor. The immune factors showing significant association with disease‐free survival (DFS) were evaluated in the total cohort (n=42).

TIICs in the preliminary population showed no significant difference between the two groups. However, CD8, CD20, CD204, FOXP3, and CD20/CD204 ratio demonstrated a tendency to act as predictive markers for recurrence. In the total cohort, significant differences were observed for CD8⁺, CD20⁺, and CD204⁺ cells in tumor islets, and CD8⁺, CD20⁺, FOXP3⁺ cells, the CD8/CD204 ratio and the CD20/CD204 ratio in the stroma, indicating their prognostic effect. The prognosis effect of the PD‐L1 expression in tumor cells could not be established, possibly associated with intratumoral heterogeneity.

CD8, CD20, and CD204 positive TIICs in stroma were identified as possible better prognostic biomarkers, considering the heterogeneity of other biomarkers. This study paves the way for exploring strategies of combination immunotherapy targeting B cell immunity in thymic carcinoma.