Breast cancer metastases to the thyroid and stomach: A case report.

The most common sites of metastasis for breast cancer are the soft tissues, bones, lungs, liver and brain; however, metastases to the gastrointestinal tract and thyroid gland from breast cancer rarely occur. The present study describes the case of a 30-year-old woman who developed gastric and thyroid metastases 5 years after her initial diagnosis of invasive ductal breast carcinoma. The initial pathological diagnosis when receiving modified radical mastectomy was invasive ductal carcinoma, and further immunohistochemical examination revealed the cancer to be estrogen receptor (-), progesterone receptor (-), human epidermal growth factor receptor 2 (HER2; ++) and Ki-67 (70%). Genetic testing indicated the HER2 amplification mutation, whereas BRCA1/2 testing was negative. A total of 21 months after surgery, during regular follow-up, the patient was revealed to have developed an enlarged lymph node in the left side of the neck and the first recurrence was confirmed. Approximately 5 years after surgery, the patient gradually developed multi-site metastasis, and developed metastases to the thyroid gland and stomach confirmed by pathology and imaging. Combined chemotherapy and targeted therapy were administered and exhibited good efficacy; however, the patient subsequently died due to heart failure. This case report describes the occurrence of gastric and thyroid metastases from breast cancer, and highlights the importance of distinguishing between metastatic and primary tumors. Distinguishing between a metastatic and primary tumor is crucial as treatment protocols vary significantly for these two types of tumors. For patients with a history of breast cancer it should first be considered whether they have metastasis of the primary disease or discomfort caused by treatment; however, the possibility of a second primary tumor cannot be ignored. If the patient has symptoms such as loss of appetite, nausea, vomiting, stomach pain and stomach discomfort, a gastroscopy should be performed in a timely manner.