What happened, in summary

A 66-year-old woman underwent excision of a repeatedly refilling cyst-like lesion in the right breast. Although a recent screening mammogram had appeared benign, pathology showed a 1.8 cm metaplastic carcinoma with squamous differentiation, lymphovascular invasion, and a high Nottingham score. The tumor was triple-negative: estrogen receptor-negative, progesterone receptor-negative, and HER2-negative.

The surgical margins were clear, and sentinel lymph-node biopsy found no cancer in any of the three removed nodes. The breast cancer was classified as stage I, pT1cN0M0. Staging PET-CT then revealed multiple nodules in the right lung. Biopsy established that these represented a separate primary lung adenocarcinoma rather than breast-cancer spread.

The multidisciplinary team selected six cycles of paclitaxel and carboplatin to treat both cancers. Radiation to the breast was omitted because its additional benefit was considered small in the setting of the synchronous multifocal lung cancer and systemic chemotherapy.

The breast and lung cancers were monitored separately. At 24 months after diagnosis, breast MRI showed no recurrent breast cancer. She described feeling well and living an active life while continuing regular blood tests, PET scans, CT scans, and breast imaging. Her case demonstrates why separate lesions need biopsy before they are assumed to be metastases from one cancer.