What happened, in summary

A 64-year-old woman first noticed a lump in her left breast in March 2024. Biopsy was initially interpreted as triple-negative invasive breast cancer. A second lesion was then found in the right breast, and she underwent bilateral nipple-sparing mastectomies with reconstruction.

Postoperative staging changed the picture. CT scans showed a spiculated lung nodule, an adrenal metastasis, and additional suspicious subcutaneous lesions. Biopsy of the lung and comparison with the breast tissue showed that the tumors were much more consistent with a primary pulmonary carcinoma that had spread to both breasts and other sites, rather than two primary breast cancers. The distant breast and adrenal involvement established metastatic lung cancer.

Molecular testing did not identify the listed common actionable lung-cancer driver alterations, and PD-L1 was negative. After the lung origin was established, carboplatin, paclitaxel, and pembrolizumab were planned as first-line systemic treatment. At that point, she remained in good general condition and asymptomatic while systemic treatment was being planned.