Ectopic creatine kinase MB production in metastatic cancer.

This case concerns the presence of high serum levels of creatine kinase MB isoenzyme in a patient with metastatic cancer. This patient did not have a myocardial infarction, so the source of the CK-MB was investigated. Because of the observation of macro-creatine kinase in patients with cancer, it was necessary to rule out the presence of this form of the enzyme. Extensive laboratory analysis demonstrated that the isoenzyme was true CK-MB, not an atypical or macro CK. Results of the study showed that ectopic production of the isoenzyme was the apparent source of the high serum activity. Homogenization of the cancer tissue demonstrated the presence of a high percentage of CK-MB activity. The implications of CK-MB production in cancer are discussed, including the use of various technics to rule out interfering activities when situations such as this occur.