Stage I triple-negative solid basaloid adenoid cystic breast cancer treated with mastectomy and oral chemotherapy

What happened, in summary

This woman had 2 separate left breast cancer histories, 10 years apart. At age 82, she underwent partial mastectomy for a Stage I luminal HER2-type invasive ductal carcinoma in the upper inner quadrant of the left breast. That earlier cancer was T1cN0M0, ER-positive, HER2-positive, and PR-negative, and she received postoperative radiotherapy, anastrozole, and trastuzumab. Ten years later, at about age 92, she noticed a new 10 mm mass in a different area of the same breast, away from the prior scar. Needle biopsy found an unclassified carcinoma, and MRI showed a 17 x 8 x 8 mm irregular enhancing mass without lymph-node or distant metastasis on imaging. She underwent left mastectomy and sentinel lymph node biopsy. The sentinel node was negative, so lymph node dissection was omitted, and she was discharged without complications on postoperative day 6. Final pathology showed solid basaloid adenoid cystic carcinoma of the breast, staged T1cN0M0, Stage I. The current tumor was triple-negative, with ER and PR non-expression and no HER2 overexpression. Ki-67 was high at about 80%, c-kit was diffusely positive, CK7 was patchy positive, and several myoepithelial, GATA3, and neuroendocrine markers were negative. Because of her advanced age, standard anthracycline- or taxane-based chemotherapy was avoided. She instead received postoperative tegafur-gimeracil-oteracil potassium. At 1 year after surgery, she was recovering well without signs of metastasis. The tumor was considered clinically distinct from the earlier breast cancer because it arose in a different quadrant, had a different biomarker profile, and showed the rare solid basaloid adenoid cystic pattern rather than recurrent invasive ductal carcinoma.