1 A rare cause of axillary swelling may be breast cancer or lymphoma. 2  The lymph nodes in the groin (femoral or inguinal lymph nodes) may swell from an injury or infection in the foot, leg, groin, or genitals.3  In rare cases, testicular cancer, lymphoma, or melanoma may cause a lump in this area. A rare cause of axillary swelling may be breast cancer or lymphoma. 2  The lymph nodes in the groin (femoral or inguinal lymph nodes) may swell from an injury or infection in the foot, leg, groin, or genitals.