bowlofbabelfish ....
"Of course taking exogenous hormones is harmful. Hormones are powerful things and drive all sorts of cellular processes - including cancers. Oestrogen in particular can be harmful in excess - even the normal physiological levels women have if they’re overweight for example are enough to drive various processes involved in cancers. "
47 years worth of studies....
Cancer Prevalence Is Not Increased in Transgender Adults Using Hormone Therapy
The overall cancer incidence in transgender men and women did not differ significantly from that in control groups in studies to date. The incidence of breast cancer in transgender individuals taking estrogen is not different from secular trends in males and is lower than secular trends in women. A rare but possible increase prostate cancer (0.04%) has been reported in transgender women, however, the findings are limited by decreased screening and the relative young age (average, 29.3 years) in subjects at the start of therapy.4
Hyperplasia in the female reproductive tract has been reported in studies that are low powered. However, newer data suggest that testosterone therapy in transgender men may be associated with tissue atrophy of the epithelium of the cervix and endometrium, not with malignancy as might have been presumed from the hyperplasia data.
It is also important to follow cancer screening guidelines for transgender individuals’ natal gender.