Lump in Arm Pits. For further treatment.

Dear madam/sir, My wife delivered a healthy male baby at 23.5 yrs and now she is 26 yrs old. She feeded the baby in both the breasts for 1 yr & 2 months. Since the age of 20 yrs she developed lumps in both of her armpits with much pain and it used reduce by itself and regrow again. After child birth, the lump is develops in any one of her armpit with much pain 3 days before start of mensuration and gets cured itself immediately by release of puzz after mensuration. Then the same gets repeated. Sometimes she feels the effect of pain till her breast and feel heavy on the side of breast. After mensuration and release of puzz, a small sist (very small ball like) like structure develops inside the armpit (inside the skin) and remains without any pain. This painless sist (or lump) sometimes dissolves itself and regrows. Requesting your valuable advise for further treatment.