[A patient with thyroid cancer evaluated according to Response Evaluation Criteria in Solid Tumors during treatment for breast cancer recurrence in hepatic and cervical lymph nodes].

We describe a case of a 69-year-old woman who underwent left breast-preserving surgery and axillary dissection for left-sided breast cancer at 60 years of age. The histopathological diagnosis was papillotubular carcinoma, luminal A (pathological T1N0M0).In the eighth year after surgery, computed tomography (CT) revealed recurrence in the liver and cervical lymph node metastasis. The patient did not respond to 3 months of treatment with letrozole (progressive disease [PD]). Six courses of chemotherapy with epirubicin and cyclophosphamide (EC) were administered. Subsequently, the attending physician was replaced while the patient was receiving paclitaxel( PTX).After 4 courses of treatment with PTX, the liver metastasis disappeared (complete response [CR]).However, the cervical lymph nodes did not shrink (PD).The cytological diagnosis was papillary thyroid cancer with associated cervical lymph node metastasis. Total thyroidectomy and D3b cervical lymph node dissection were performed. The pathological diagnosis was pEx0T1bN1Mx, pStage IVA disease. Replacement of the attending physician is a critical turning point for patients. During chemotherapy or hormone therapy for breast cancer, each organ should be evaluated according to Response Evaluation Criteria in Solid Tumors (RECIST).In the case of our patient, thyroid cancer was diagnosed according to RECIST. Cancer specialists should bear in mind that the treatment policy may change dramatically depending on the results of RECIST assessment.