Recurrent Lobular Breast Cancer Spread to the Opposite Armpit Lymph Node

What happened, in summary

A 62-year-old woman was found to have a small, non-palpable abnormality in the upper outer part of her left breast during routine screening. A biopsy confirmed invasive lobular carcinoma. This was a recurrence: 11 years earlier, she had been treated for a 12 mm mixed lobular cancer and ductal carcinoma in situ in the same breast. That earlier cancer was ER-positive, PR-positive and HER2-negative and had involved 2 sentinel lymph nodes. Her treatment had included breast-conserving surgery, axillary surgery, chemotherapy, radiation and anastrozole. She then completed 5 years of uneventful surveillance.

For the new cancer, she was scheduled for a left mastectomy. Before surgery, lymphatic mapping unexpectedly showed drainage from the left breast to the right armpit, probably because previous breast and axillary treatment had changed the usual lymph pathways. The surgical team therefore sampled a right axillary sentinel node with her agreement.

Final pathology showed a 70 mm grade 3 invasive lobular carcinoma with focal ductal carcinoma in situ and clear margins. The tumor remained ER-positive, PR-positive and HER2-negative. The right sentinel node contained a large breast cancer metastasis, although examination and imaging found no cancer in the right breast and PET/CT found no other distant spread.

Under current staging rules, cancer in the opposite axillary nodes is classified as stage 4, although specialists debate whether it can behave more like regional disease when lymph drainage has been rerouted by earlier treatment. The patient chose right axillary clearance and a preventive right mastectomy, partly because of imbalance and functional problems after the left mastectomy. She then proceeded with adjuvant chemotherapy.