I noticed (in the archive post) that the women complaining of breast pain were in a similar age range - 60 yrs and having experienced a problem over the past few years. Could the onset of menopause have an effect?
Also, the affected women all listed "large" breasts. Could the increased fat content make a difference?
One other suggestion was the wetsuit being too tight under the arms affecting the lymph nodes drainage while under pressure. Since most wetsuits are cut for men, that could make a difference. I have to buy mens' suits because of height (6'0") and inseam (36"). I have had the boobs squished a bit (a lot) to have the suit fit every where else. (until I got a Henderson hyperstretch.)
In regard to pressure, I've gotten bruises/petichiae from mammograms. From diving, not yet.
These could all be possibilities to discuss with a DR. Make sure you find an MD who understands diving,though, not just any MD.