Macrophages in skin cancer: quantitative and functional studies

The number of tumor-infiltrating macrophages was estimated in 43 patients with skin cancer, including 18 cases of squamous cell and 25 cases of basal cell carcinoma. Macrophages were identified in cell cultures by 2 assays, namely phagocytosis and resistance to detachment by trypsin. The average percentage of adherent cells for the 2 groups of skin tumors was 4.5 +/- 2.6 and 10.2 +/- 5.2, respectively, and the difference was statistically significant. Follow-up studies after surgical excision of the primary neoplasm showed a relatively low macrophage content in 2 of the 4 cases in which local recurrences occurred. Preliminary functional studies suggested that soluble factors may be released by neoplastic cells, accounting for the inhibitory effect of tumor cell supernatants on macrophage chemotaxis in vitro.