Acid phosphatase (acid phosphatase, ACP) is widely distributed throughout various tissues, mainly in the lysosomes of cells, so it is often used as a lysosomal marker enzyme. Acid phosphatase outside the lysosome exists in the endoplasmic reticulum and cytoplasm, acid phosphatase in various animals are different, acid phosphatase is suitable for pH 4.5 ~ 5.5.

Acid phosphatase staining solution (lead nitrate method) to β-glycerophosphate sodium as a substrate, in the acidic pH of acid phosphatase hydroxylated to release phosphates, lead ions are generated when lead phosphate precipitates, and then by the S2 + replacement, and ultimately generate Lead sulfide brownish-black precipitate, acid phosphatase inhibitors for fluoride, phosphate ions in general. For some acid phosphatase, Cu2+, tartaric acid ion and carbon tetrachloride and aldehydes are also inhibitors, Mn2+ is the activator of the enzyme, frozen section and paraffin section can be used, but most of them are frozen section, clinically the staining method is strongly positive for prostate cancer and metastatic prostate cancer of other organs, and the tumor cytoplasm of Hodgkin's lymphoma, gastric carcinoma, lung carcinoma, breast carcinoma, epidermoid carcinoma of tongue, multinucleated giant cell tumor is also positive. The tumor cytoplasm of Hodgkin's lymphoma, gastric cancer, lung cancer, breast cancer, epidermoid carcinoma of the tongue, multinucleated giant cell tumor also showed strong positive reaction, and Ewing's sarcoma and osteogenic sarcoma were negative.