How to talk to a one night stand about her potential breast lumps issues?

A significant element with breast lumps is whether they're painful or uncomfortable to touch. Or at least more so than someone generally poking at soft tissue! So instead of asking "Is that normal?", maybe ask "Does that feel uncomfortable? I'm asking because..."

It's not something you can easily mention right now, or perhaps even at the next date. You really don't want to throw in a passion-killer like that on a date!

But if things go "further" in future, then after sex (NOT straight after, but maybe while you're getting dressed?) might be a time when she's not embarrassed at you feeling her breasts, and where you can talk about intimate things like that.

You might consider sharing your findings with a discussion of a personal/family history of a medical encounter or preventative screening. I disagree about the importance of information over tone. Tone is incredibly important in discussing breast health, particularly in the context of your encounter. She may view this a negative commentary on her breasts. Interpretation is highly variable and any factual data you give will be colored dramatically by her emotional interpretation.

If you are not a physician or medical provider, the data you provide should be scant and heavily framed in the context of your concern. Then there should be a lot of listening, acknowledgment and understanding of what she expresses.

Statistically, any lump in that age group w/o a strong family hx, BRCA1/2, or other genetic disease is overwhelmingly likely to be a cyst, fibroadenoma or fibrocystic change.

Keep in mind that the angst generated by any breast disease is far out of proportion to what you would anticipate as a man. This includes the anxiety associated with workup and the common associated false positives.

I mention one last thing as an aside. Last I read, there actually has been no study showing breast self exam is effective in decreasing morbidity and mortality. Someone feel free to correct me as I have not combed cochrane recently. Much of what is "standard of care" in medicine has no factual basis, but then again, there has never been a double blind study showing parachutes prevent injury from gravitational challenge (look it up in the BMJ).

This is going to be uncomfortable, for the both of you. Albeit, it'd be so much more uncomfortable for her if you never told her and she had to find out on her own.

I suggest you tell her you have something important to say, and lead with the fact that it may be uncomfortable. Explain your concern, about what you've felt, and explain that it may be minor. Suggest that you'd feel much better if she were to have them examined, out of concern for her health and safety.

First of all this won't be a pleasant conversation - and it does not have to be. This is one of the occasions where the information matters more than the tone. Think of it this way: If it is serious, you may save her life!

Just inform her that you found these lumps to be unusual. Ask her if she had this inspected. If not, then tell her that she absolutely needs to get this checked. You can try to soften the blow, by mentioning the very likely just benign nodules/cysts line, but leave absolutely no doubt that this has to be checked by a doctor ASAP!

You can also remind her that such a screening is, at a first step, a quick and harmless ultrasound inspection. If there is something suspicious, the doctors will take it from there.

Remember, chances are high you have handled more breasts than she has, so she might not be aware she has something unusual.

(Experience: Having breast cancer in my circle and also a woman who counts as a risk candidate and has to get regular screenings)