Breast Cancer Metastasis to the Parotid: A Case Report with Imaging Findings

Objective: Rare disease Background: Metastasis to the salivary gland is rare, with the parotid being the most commonly involved site among the salivary glands. Breast cancer metastasis to the parotid gland has been rarely reported in the literature, and relatively few case reports have described the imaging findings. Case Report: A 59-year-old woman presented with a recently growing mass in the left parotid gland. She had a past history of left breast cancer 6 years ago, treated by left modified radical mastectomy with axillary lymph node dissection followed by adjuvant chemotherapy, radiation therapy, and trastuzumab. During follow-up, multiple metastases developed and the patient was subsequently treated with palliative chemotherapy. Neck ultrasonography revealed a heterogeneous echoic mass with indistinct margins, irregular shape, and weak rim vascularity in the left parotid gland. Contrast-enhanced neck computed tomography revealed an irregular mass with heterogeneous enhancement in the inferior pole of the left parotid gland. Ultrasonography-guided 18-gauge core needle biopsy was performed, and the histopathology report was metastasis from ductal carcinoma of breast with positive expression of human epidermal growth factor receptor 2 and negative expression of estrogen receptor, progesterone receptor, and androgen receptor. Despite palliative chemotherapy and trastuzumab, the patient died 2 months after the diagnosis of metastasis to the parotid gland. Conclusions: We report a rare case of metastasis from breast cancer to the parotid gland, with imaging findings including neck ultrasonography and contrast-enhanced neck computed tomography. Breast cancer rarely metastasizes to the parotid gland, but radiologists should be aware of this possibility, especially in patients with a prior history of breast cancer.