Radioimmunoassay of human epidermal growth factor in human breast cyst fluid.

Epidermal growth factor (EGF) was assayed radioimmunologically in three secretions of the human mammary gland: milk (n = 16), colostrum (n = 8) and breast cyst fluid (n = 139). The immunoreactivity (immunoreactive EGF) detected in these three fluids corresponds directly to monomeric EGF, as can be shown by the complete cross-reaction with the standard and the identical behaviour in chromatography on Sephadex G50. The mean concentration of EGF is significantly greater in breast cyst fluid (241 +/- 143 ng/ml) and in colostrum (197 +/- 56 ng/ml) than in milk (107 +/- 22 ng/ml). The range of individual values in cyst fluid is large, 5-945 ng/ml. A possible role of EGF as a paracrine or autocrine factor in the pathology of cystic dysplasia of the mammary gland and in the increased risk of malignant transformation is hypothesised.