Immunohistochemistry and fluorescent in situ hybridization are techniques that help identify the primary site of metastatic cancers and define disease subtypes through detection of protein markers and genetic translocations. Both techniques guide therapy decisions and provide prognostic information. Immunohistochemistry works similarly to ELISA by detecting antibodies bound to tumor cell antigens, while fluorescent in situ hybridization uses fluorescent DNA probes to detect genetic abnormalities. Flow cytometry also analyzes cellular markers like CD34, CD10 and CD19 to diagnose cancers such as acute lymphoblastic leukemia and monitor minimal residual disease following treatment.