In general terms the larger a lesion is the more likely you are to find nodal metastases. In practice however, you will be amazed by how many large lesions have a negative sentinel node and how many small lesions have a positive sentinel node.
The co-morbidity of open axilla dissections is avoided. The significant complication of lymphoedema is now (luckily) a thing of the past. This was a very serious and debilitating complication is the days of radical mastectomies.