Parotid Metastasis 10 Years After Initial Diagnosis of HER2 Positive Breast Cancer: A Case Report

Abstract The parotid gland is a rare site of metastatic disease in human epidermal growth factor receptor 2 (HER2) positive breast cancer. It often presents as a painless enlarging mass at the angle of the jaw; however, rarely it can be associated with facial nerve palsy. There is no consensus regarding the best approach to managing these uncommon metastases. We report the case of a patient with metastatic HER2 positive breast cancer who developed oligoprogressive disease with a parotid metastasis over 10 years after initial diagnosis of metastatic disease. There are only 5 reported cases of HER2 positive breast cancer with parotid metastases. Our patient underwent treatment with palliative radiotherapy, followed by the continuation of her HER2 targeted systemic therapy with good effect. This case is significant due to the lengthy period (10 years) after initial diagnosis that the metastasis appeared, the treatment the patient received for it (radiation) and the available overall survival and progression-free survival data from time of parotid metastasis diagnosis.