Luminal A solid papillary breast carcinoma with lung metastasis: mastectomy and lung resection, PET-CT clear

What happened, in summary

A 53-year-old perimenopausal woman first underwent left mastectomy for a very small breast lesion measuring 0.3 cm. Pathology showed intraductal solid papillary carcinoma. The tumor was hormone-receptor positive, with ER greater than 80% and PR 40%, HER2 0, Ki-67 15%, synaptophysin positivity, calponin-positive myoepithelial cells, and CK5/6 negativity. No additional treatment was given after breast surgery. Five years later, routine chest CT showed a tiny right lower-lobe lung nodule about 1 mm in diameter. Continued imaging showed slow growth: 4 x 4 mm at 6 years and 3 months after mastectomy, then 15 x 13 mm at 7 years and 8 months. Several small bilateral lung nodules were also seen, with no definite enhancement on contrast imaging, but physical examination, blood count, coagulation, liver and kidney function, and tumor marker testing did not reveal another primary cancer, infectious disease history, or any known genetic disorder preoperatively. Because the enlarging nodule was concerning, she underwent lung tumor resection. Pathology showed a gray-white tumor with solid nodules, fibrous vascular axes, mucus, and neuroendocrine differentiation. Immunohistochemistry of the lung lesion showed ER 90%, PR 80%, HER2 0, Ki-67 15%, chromogranin A and synaptophysin positivity, TTF-1 negativity, and GATA3 positivity. These findings supported metastatic breast origin rather than primary lung cancer, with Luminal A biology. After lobectomy, she received postoperative antibiotics, and the incision healed well. PET-CT about 40 days later showed no abnormalities. Her specialist recommended regular follow-up without additional antitumor drug therapy, and she was alive and in good condition.