Small bilateral axillary lymph nodes and neck all less than cm, last 5 months. all investigated nil cause found, tho never biopsied now new left breast lump 6 oclock, approx 2cm x 1cm, could it be lymphoma? screening mammogram 2 months ago normal?

With a breast mass of "2cmx1cm", a biopsy is necessary to determine the diagnosis, which is usually accompanied by an axillary "sentinel node" biopsy on the side of the dominant breast mass.

You lymph nodes are in all likelihood normal. The breast lump needs to be evaluated. For the lymph nodes - You may feel the nodes every couple of weeks, if any of the lymph glands doubles in size, becomes painful, ulcerates, or other nodes become enlarged, or you develop fever, or lose weight, you should see a doctor. Wish you good health!