The right superficial parotid mass in this case first came to the patient's attention when he began having trouble sleeping on the right side. The mass was mildly tender to palpation, but there were no paresthesias or other evidence of facial nerve injury.

Imaging with CT demonstrated the cystic and solid lesion above without lymphadenopathy, and the subsequent MRI showed a similar mass, but more clearly demonstrated enhancement in the solid components of the mass. The mass was then referred for FNA and core biopsy under ultrasound guidance. The ultrasound appearance of the cystic and solid mass is relatively nonspecific.

Pre-biopsy, the differential for the mass is still relatively wide and "tissue is the issue."  Possible etiologies include:

• Warthin tumor
• adenoid cystic carcinoma
• pleomorphic adenoma
• mucoepidermoid carcinoma
• acinic cell carcinoma

During the FNA, the cytopathologist remarked that all the smears he was seeing "looked just like acinar cells." On the core biopsy, a diagnosis of acinic cell carcinoma was made, a rare diagnosis.