This is a very general question. however, to diagnose recurrence of a breast cancer;
1.History of the patient; for example feeling a lump in the breast or armpit, back or groin pain, shortness of breath, loss of weight, extra
2. Proper examination by a breast specialist
3. investigation; Mammogram, ultrasound, and MRI for local recurrence in the breast and the armpit.
for the spread of cancer outside the breast and armpit, and only in the presence of symptoms, for example back or groin pain, shortness of breath. Then investigation like CT scan, bone scan, PET scan, MRI will be required