As I'm sure you know, breast cancer is pretty rare at your age, but not
unheard of.

I dare say Kaye, our resident 'lobular' queen, would like me to say that the
symptoms are a possible for lobular bc, but its reaction to the menstrual
cycle makes it more likely to be something benign.

If it doesn't appear to have grown in three years, that is another
indication against cancer, one would expect visible growth in that time even
in a pretty slow growing tumour.

Mammograms in younger women are often inconclusive due to the natural
density of the breast tissue.  I'm pretty sure that the mammogram will image
the area you are worried about though, the 'tail' of the breast.  If it was
inconclusive they should have said so.

If you want to be certain, yes you could request an ultrasound, and the
final resort would be a biopsy, where they use a hollow needle or similar
tool to take a small sample of the lump and examine it under a microscope to
see what it is made of.  The disadvantages of that is that there is a small
risk of infection, and that the resulting scar tissue may show us as
something suspicious on future mammograms.

There is also the expensive options of a PET scan, which has better
discrimination than a mammogram, but involves a significant radiation dose.
And maybe an MRI scan, which is harmless, but I don't know how much it would
help.  It's good for finding small lumps you can't feel, but here will
probably just tell you what you already know.  And it tends to find lots of
harmless things too.

Tim Jackson