Lymphnodes in axillary region (as a matter,,anywhere) mostly get enlarged and become palpable (toucheable) to our hands....mostly due to a primary source of infection nearby....in ur case it cud be infection within breast tissue or upper limb.....but however the problem becomes bigger if they appear..."hard" or continuously enlarging and are multiple on both sides(armpits)...and in other regions like neck and groin regions......In these situations....a malignancy(cancer) arising within lymph nodes(lymphoma) or arising elsewhere (in ur case breast mass shud be looked upon as a possible source).must be searched for.......However....a Gen.surgeon needs to examine u carefully and with help of some investigations like FNAC or Excision Biopsy from the node, an accurate diagnosis can be made easily and treatments started as required....

Regards

Dr Rakesh Akula MS