We found fundamental differences in the gene expression of cellular infiltrates derived from scaffolds in tumor-bearing versus non-tumor mice, with a tumor-specific signature including Chil3, Trem2, C1qa, and C1qb. Single-cell RNA sequencing identified changes primarily in macrophage gene expression and revealed two distinct populations of macrophages that were unique to tumor-bearing animals. The gene discussed is TREM2; the disease is neoplasm.