It is not always necessary to do axillary dissection for T1 and T2 breast cancer--point. 
Axillary lymph node dissection (ALND) has been a part of breast cancer management since the 1900s.  The idea that axillary metastases do not require surgical removal is a repudiation of the Halstedian concept of breast cancer biology, yet multiple prospective randomized studies show that the incidence of nodal recurrence in patients not having ALND is substantially lower than expected, based on the incidence of axillary metastases in patients having ALND, and survival does not differ based on axillary treatment.  Avoidance of axillary dissection significantly reduces the morbidity of breast cancer surgery.  As the use of systemic therapy has increased and targeted therapies have become available, the incidence of axillary recurrence in patients not having dissection has decreased to approximately 1% at 5 years, making routine axillary dissection difficult to justify.  ALND is no longer standard management for patients with T1 and T2, clinically node-negative cancers undergoing breast-conserving therapy and found to have a positive sentinel node, and can also be avoided in patients with these tumor features having mastectomy if the need for postmastectomy radiotherapy is clear with the finding of a positive sentinel node.