Receptor conversion between primary and metastatic breast cancer occurs in up to 32% of patients, resulting in ineffective therapy in the absence of corresponding biomarkers. Prompt reassessment of these biomarkers at the time of disease progression can help optimize treatment decisions.
We report the case of a 59-year old Filipino woman who had a 2-month history of hoarseness. Seven years ago, she was diagnosed with stage 1B moderately differentiated invasive ductal carcinoma of the left breast, ER/PR-positive and negative for HER2 overexpression. She underwent left breast lumpectomy with axillary lymph node dissection. Oncotype DX and BRCA1/BRCA2 testing were not performed. She was treated with adjuvant chemotherapy with six cycles of doxorubicin, cyclophosphamide and docetaxel. This was followed by adjuvant radiation therapy and institution of daily letrozole. Physical examination revealed no palpable breast masses nor lymph nodes.
Laryngoscopy demonstrated persistent glottic gap during phonation with an immobile right vocal fold at the paramedian position, consistent with right vocal cord paralysis.
Whole body PET-CT scan revealed hypermetabolic right level IV cervical lymph node measuring 0.6 cm and hypermetabolic right paraaortic and right paratracheal lymph nodes, measuring 0.8 and 1.1 cm respectively, worrisome for metastasis. No other hypermetabolic foci were seen.
Excision biopsy of the right cervical lymph node confirmed tumor cells consistent with metastatic carcinoma. IHC showed tumor cells positive for GATA3 and mammaglobin, supporting the diagnosis of a breast primary. Breast panel of the excised cervical lymph node revealed ER-positive, PR-negative, and HER2-positive. Subsequent metastatic workup was unremarkable.
Given the involvement of non-contiguous lymph nodes, she was treated as a case of ER-positive, HER2-positive metastatic breast cancer. She was not amenable to cytotoxic chemotherapy and preferred treatment with the least possible side effects, thus targeted therapy with ado-trastuzumab emtansine (TDM-1) every 3 weeks was instituted. After her third session of TDM-1, interval PET-CT scan showed 27% regression in the size of the right paratracheal lymph node.