Expression of Immune Checkpoint-Associated Proteins for CD24, Siglec-10, CD47, and SIRPα in Breast Phyllodes Tumor

This study aimed to investigate the expression of immune checkpoint-associated proteins in phyllodes tumors (PTs) and assess their clinicopathologic and prognostic significance. Surgical resection specimens from 200 patients were included, and the expressions of CD24, Siglec-10, CD47, and SIRPα in both the epithelial and stromal components of the tumor were assessed, with ≥1% positivity considered positive. Of 200 cases, 145 were benign, 44 borderline, and 11 malignant. The expressions of CD24, Siglec-10, CD47, and SIRPα in stromal cells increased with tumor grade: CD24 was associated with stromal cellularity, atypia, and mitosis; Siglec-10 with stromal cellularity and atypia; CD47 with stromal atypia and mitosis; and SIRPα with stromal overgrowth and atypia. While expressions of CD24, CD47, and SIRPα were associated with either shorter disease-free survival (DFS) or shorter overall survival, multivariate analysis identified stromal CD24 expression as an independent predictor of shorter DFS. Immune checkpoint-associated proteins, particularly stromal CD24, CD47, and SIRPα, are associated with adverse features and poor outcomes in PTs, implicating potential prognostic and therapeutic relevance.