Fine needle aspiration of an unusual malignant mixed tumor in the parotid gland

The use of fine needle aspiration (FNA) biopsy in the triage of salivary gland tumors has been well established. The sensitivity and specificity of FNA biopsy for tumor diagnosis is generally very good. However, the diagnosis can be challenging due to the limited amount of tissue sampled, the occasional overlapping tumor morphology, and the presence of a malignant counterpart of a benign tumor.

FNA biopsy was performed with ultrasound guidance. Air-dried slides and alcohol-fixed slides were made for Diff-Quik staining and Papanicolaou staining, respectively. The syringes were rinsed and a cell block was prepared. The resected specimen was fixed in 10% formalin and processed by routine histology techniques.

We report a rare case of a salivary gland neoplasm with 2 distinct components: adenoid cystic carcinoma and pleomorphic adenoma. These 2 components are clearly identifiable in both cytological materials from fine needle aspiration and histological analysis of surgical resection.

Pleomorphic adenoma is the most common salivary gland tumor for patients in all age groups. The characteristic cytological feature is fibrillary extracellular matrix intermixed with epithelial cells. Malignant transformation occurs in 5% to 10% of cases. Rarely, pleomorphic adenoma exists as one component of a hybrid tumor. The surgical resection will be needed in those cases. The final diagnosis relies on the combination of the clinical information, histological findings and molecular study.