Breast invasive lobular carcinoma metastatic to the endometrium: hysterectomy and hormone therapy

What happened, in summary

A 56-year-old postmenopausal woman developed persistent abnormal uterine bleeding for 2 months. She had a history of left breast cancer treated 5 years earlier with mastectomy and axillary lymph-node dissection. The original tumor was grade III infiltrating lobular carcinoma, and 19 of 24 lymph nodes were positive. The original pathology documented heavy nodal involvement but did not provide a complete AJCC stage for the first breast-cancer diagnosis. The tumor was strongly hormone receptor-positive, HER2-negative, and Ki-67 was 25%. After surgery, she received 3 cycles of fluorouracil, epirubicin, and cyclophosphamide, followed by 3 cycles of docetaxel. She also had radiotherapy to the chest wall and supra-/subclavicular regions, with a total dose of 45 Gy, and then tamoxifen for 5 years. When she presented with bleeding, mammography and breast ultrasound were normal, but pelvic ultrasound and hysteroscopy showed a bloody endometrial polyp. Biopsy found adenocarcinoma whose features matched the prior breast carcinoma. Immunohistochemistry showed CKAE1/AE2 positivity, E-cadherin positivity, GATA3 positivity, ER positivity, PR negativity, mammaglobin negativity, and HER2 score 0, supporting metastatic lobular breast carcinoma in the endometrium. MRI showed an endometrial lesion without myometrial extension or lymph-node involvement, and PET scan did not show other lesions. The polyp measured about 25 mm at hysteroscopy and 17 x 5 x 15 mm on final pathology. She underwent total hysterectomy with bilateral adnexectomy, recovered well, and started hormonal treatment. At 18 months of monitoring, no recurrence was reported. Follow-up was scheduled every 3 months during the first year and every 6 months for the following 2 years, reflecting the need for surveillance after metastatic endometrial involvement.