Differentiation of macrophages from Lewis lung carcinoma tumour cells in tissue sections by their alpha-naphthyl butyrate esterase activity.

The activities of alpha-naphthyl butyrate esterase, non-specific esterase, indoxyl esterase and acid phosphatase were studied histochemically in macrophages in cultures and in tissue sections of primary tumours and metastases of Lewis lung carcinoma (3LL). All macrophages in culture were stained by the alpha-naphthyl butyrate esterase procedure. In tissue sections, macrophages were intensely stained by the butyrate esterase procedure, while the tumour cells were not stained at all; macrophages were easily differentiated from 3LL cells. Non-specific esterase was evident in both tumour cells and macrophages. Indoxyl esterase and acid phosphatase were present in macrophages at the margin of the tumour only. The alpha-naphthyl butyrate esterase-positive macrophages differed in shape and location from acid phosphatase and indoxyl esterase-positive macrophages. This may indicate a difference in characteristics between macrophages found inside a tumour and those found at the tumour margins.