Elevated serum alpha fetoprotein levels in postmenopausal women with primary breast carcinoma

Elevated serum alpha fetoprotein (AFP) levels were detected and measured by a RIA in postmenopausal women with primary breast carcinoma. This increased AFP consisted of both free and total AFP measured before and after treatment of serum with 0.4 M KCl. The difference between free and total serum AFP in breast cancer patients was 44 IU ml-1. We conclude that serum from breast cancer patients contains appreciable amounts of previously undetected, initially nonimmunoreactive, AFP which became immunoreactive and measurable after KCl treatment. Previous reports indicating the presence of free and nonimmunoreactive AFP in primary breast cancer tissue cytosol and synthesis of these AFP components by MCF-7 cultured human breast cancer cells supports the conclusion that elevated serum AFP measured in breast cancer patients originates from the breast cancer cells. The conclusion that AFP is a breast tumour marker protein suggests that: (1) serial serum AFP measurements in breast cancer patients may provide useful diagnostic and prognostic information in individual cases and (2) a similar nonimmunoreactive serum AFP may be detected in patients with other types of cancer not currently known to be associated with AFP.