Were there estrogen receptors on the cancer cells?  If so, breastfeeding
reduces estrogen levels and may be protective for this mom.

I have had one situation in which the birth mother supplied milk for 6
weeks.  The adoptive mother was her sister.  It was an emotionally
difficult situation anyway, but did not seem to add to the birth
mother's distress.

There is no disease concern with banked human milk, donors are screened
and the milk is pasteurized.  I have had clients get at least some
banked milk for adoptive babies.

Seeing as mom had a miscarriage (sorry), her chance of making
substantial milk is increased over a woman who has never been pregnant.
  Adoptive moms who had been pregnant (however briefly) in my practice
who pumped for 6-12 weeks before the arrival of the baby, then used a
tube supplementer device at breast afterward, were able to make between
half and three quarters of the milk that the baby needed.  One even made
a complete supply.  This is significant.  Most adoptive moms who had
never been pregnant made very small quantities.

Breastfeeding has been shown to be protective against breast cancer.
Breastfeeding is opposite from pregnancy, hormonally.  Pregnancy can be
touchy for a woman with estrogen receptor positive tumors.  I don't know
if tamoxifen would make a difference at all.  That's a question for Tom
Hale.
Best of luck, whatever you decide.
--
Catherine Watson Genna, IBCLC  New York City  mailto:[log in to unmask]

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