The macrophage content of some human tumours.

The number of macrophages present in 44 surgically removed breast tumours and melanomas was determined by making a cell suspension and measuring the proportion of cells which bound a heterologous anti-macrophage serum and spread rapidly in culture. The macrophage content of the different tumours ranged from 0% to 30%. The malignant tumours which were known to have metastasized, as well as metastatic lesions, all contained less than 10% of macrophages whereas cancers for which there was no evidence of spread at operation had widely varying numbers of macrophages.