Certain cancers types are stimulated directly by estrogen, and in those cancer cells the hormone actually acts to upregulate its receptor. So the
more hormone the more the response. The receptor then mediates some signaling in the cell replication pathway. The actual mutation or genetic
predisposition is in the estrogen receptor gene and causes it to be made without much control. This will usually happen later in life because of
something called the two hit hypothesis, where even if someone has one bad copy of the gene the other can make up for it until it is hit by a mutation
event and made made as well. So if two bad genes you will probably get cancer anyway, with one bad gene a large dose of estrogen will act to
upregulate the cancerous gene even more. Fortunately these types of cancer can be blocked with estrogen receptor blocking chemotherapy like
Methotrexate.

