How is immunohistochemistry used in cancer dx?

Powerful, determines origin of metastasis, like cytokeratin differentiate large cell lymphoma than undifferentiated carcinoma, PSA in prostatic origin. Some therapeutic like immunocytochemical detection of ER/PR in breast cancer. Use monoclonal Ab specific for cellular component, all serum markers, Tg, S100 (melanoma), Actin (muscle), CD (lymphoma), estrogen receptor (breast cancer), intermediate filaments.