Good question. We have a lot of
lumpsLumps in the breasts under the skin which we stumble upon only by accident, just as you describe. When I was in the second year of medical school, afflicted with the hypochondria typical of that stage of training, I found any number of lumps in that way. Each threw me into a panic, which in turn propelled me to a doctor for reassurance.
In the location of your lump, the most common type is a lipoma, a collection of fat cells. These are rubbery and move around under the finger. Quite benign and worthy of being ignored.
Obviously, proper diagnosis requires that you be examined in person, which is what I recommend you do.
Best.
Dr. Rockoff