Widely Metastatic Parotid Acinic Cell Carcinoma to Bone and Liver: A Case Report, Review of Literature, and Review of Diagnostic Challenges

Distant metastasis of salivary gland neoplasms is a rare occurrence. Generally, high-grade salivary malignancies such as salivary duct carcinoma and high-grade mucoepidermoid carcinoma, as well as tumors located in the submandibular gland, show a higher likelihood of metastasizing. Acinic cell carcinoma is an uncommon salivary gland neoplasm that typically occurs in the parotid gland and is considered a low-grade malignancy. Metastasis is unusual and, if present, predominantly involves the lung and bones. However, vertebral metastasis is exceedingly rare. Here, we describe a rare case of recurrent acinic cell carcinoma of the parotid gland with widespread metastases to multiple bones, including the vertebrae, and to the liver, which was diagnosed in part by cytology. To our knowledge, this is the first report in the cytology literature to describe salivary gland acinic cell carcinoma with metastases to such distant sites and to discuss the resulting cytologic differential diagnoses.