I liked your link
Sorry I wasn't here when you posted it. I was sick, and then busy with doctors.
I, too, have a mysterious lump in one of my mammary glands.
Despite the fact that it has been palpable (and sore) for several years, it has consistently failed to show up on either x-ray or ultrasound. (The Invisible Lump!
That, plus the fact that it is veeeeeery slow-growing, led the breast surgeon to decide that it is likely glandular tissue or something else benign.
But she wants me to go for a fine-needle biopsy anyway.