Neuroendocrine abnormalities and the pathogenesis of estrogen-receptor-positive breast cancer.

Breast cancer in women appears to have different manifestations, depending on the presence or absence of the estrogen receptor (ER) . Although both ER-negative and ERpositive breast cancers are likely to be associated with the presence of an oncogene, ERpositive breast cancer is also associated with two clinical neuroendocrine abnormalities involving the pineal gland and olfaction, both of which may result from a defect in tryptophan metabolism along the kynurenine pathway . Recent studies of the epidemiology, genetics, and endocrinology of breast cancer suggest that this neoplasm occurs in at least two distinct forms, depending on estrogen receptor (ER) status .