What happened, in summary

Five years after treatment for left-breast adenoid cystic carcinoma, a 60-year-old woman noticed a painless 2 cm mass in the right axilla. She had known ectopic breast tissue in that area, which had previously shown atypical ductal hyperplasia. Ultrasound identified a solid lesion, and excision confirmed a new primary cancer arising in accessory breast tissue. Pathology showed a 1.5 cm grade II invasive ductal carcinoma with an associated 12 mm grade III ductal carcinoma in situ. Surgical margins were negative and the skin was not involved. The invasive tumor was ER-positive and PR-positive at greater than 90%, HER2-negative, and had a Ki-67 index of 20%. The pathologic classification was pT1c Nx M0. Sentinel-node biopsy was attempted, but no node was identified; clinical and imaging assessment showed no axillary nodal disease. Her Oncotype DX recurrence score was 17, so chemotherapy was not recommended. She recovered well after wide local excision, with a healed incision, normal shoulder movement, and no lymphedema. Radiation to the axillary tumor bed and anastrozole were scheduled. She said the second diagnosis was frustrating after prior bilateral mastectomy and careful surveillance, but she was grateful it had been found before spread.