Metastasis to the thyroid gland from primary breast cancer presenting as diffuse goiter: A case report and review of literature

BACKGROUND Metastasis to the thyroid gland (TM) from primary breast cancer is uncommon and usually presents as thyroid nodules; however, diffuse goiter without thyroid nodules is the first sign of TM in rare cases. Skip metastases (SMs) to the lymph nodes in breast cancer, defined as discontiguous higher-level metastases in the absence of lower levels of contiguous metastases, have been reported in the contralateral cervical area of the primary tumor site in rare cases. CASE SUMMARY A 49-year-old previously healthy Chinese woman was diagnosed with right lateral invasive ductal carcinoma and underwent neoadjuvant chemotherapy treatment and bilateral mastectomy with axillary lymph node dissection. No malignancy of the left breast or axillary or distant metastases were identified preoperatively. However, enlarged left cervical lymph nodes were detected 36 mo after surgery, and rapidly enlarging thyroid glands without nodules were detected 42 mo after surgery. Fine-needle aspiration cytology was performed on the left cervical lymph nodes and left lobe of the thyroid, which were both revealed to contain metastases from the primary breast cancer. Additionally, the immunostaining profiles changed in the process of metastases. The patient was discharged with the NP (vinorelbine and cisplatin) regimen for subsequent treatment, and stable disease was determined when the curative effect was evaluated. CONCLUSION Diffuse goiter may be the first sign of TM, and enlarged lymph nodes in the contralateral cervical area may be SMs of primary breast cancer.