Why does my breast tissue extend into my armpit? is this normal?

May be normal.: One's doctor can carefully examine the breasts and armpits to see it they feel normal. Breasts normally extend towards the armpits, but if a woman has swelling in her armpit area each time she has a baby and breastfeeds, she might have some extra breast tissue (milk-producing glands) in the armpit area. That would be an "extra" breast, a small lump without an extra nipple.