Macrophages in human tumours: an immunohistochemical study.

Forty-five human malignant tumours and three benign lesions were stained histochemically for non-specific esterase (NSE) and acid phosphatase (AP), and immunohistochemically for lysozyme. Most of the tumours contained small numbers of lysozyme positive macrophages (LPM), but colonic tumours showed moderate numbers of LPM around the edge of the lesions. Gastric and secondary duodenal tumours (n = 3) contained moderate numbers of intralesional LPM in addition. Most squamous and all mesenchymal tumours contained no lysozyme positive macrophages. The usefulness of the three staining methods was assessed and it was concluded that lysozyme was specific but detected only part of the macrophage population. Neutrophil polymorphs were also stained but could be recognised by nuclear morphology. AP and NSE detected more cells but stained tumour cells as well as macrophages, making these methods of limited use in tumours showing invasion of the stroma by single cells or small groups of cells.