Pleomorphic adenoma of the major salivary glands: diagnostic utility of FNAB and MRI.

OBJECTIVES/HYPOTHESIS: Pleomorphic adenoma (PA) is the most common, benign tumor of the major salivary glands. Surgical resection is the treatment of choice. Initial preoperative workup of major salivary gland neoplasms often includes fine needle aspiration biopsy (FNAB) and magnetic resonance imaging (MRI) of the head and neck. Our objective was to assess the positive predictive value of FNAB and MRI in the evaluation of PA arising from within the major salivary glands.

STUDY DESIGN: Retrospective chart review.

METHODS: All patients with a FNAB diagnosis of PA of the major salivary glands and who underwent surgical excision at our institution from 2001 to 2011 were identified. FNAB slides from these cases were reviewed by a cytopathologist for findings suggestive of PA: fibrillary stroma, mesenchymal elements, plasmacytoid myoepithelial cells, epithelial cells forming ducts or tubules, and the absence of nuclear atypia. For those patients with a preoperative MRI, the MRI studies were reviewed by a neuroradiologist for findings suggestive of PA, including homogenous T2 hyperintensity, well-circumscribed borders, and solid contrast enhancement. Positive predictive value (PPV) of these specific FNAB and MRI findings were calculated using chi-squared testing.

RESULTS: One hundred forty-six patients met inclusion criteria, and 68 had preoperative MRI. PPV of a FNAB diagnosis of PA was 97.8%. Characteristic features of PA on FNAB (fibrillary stroma, mesenchymal elements, plasmacytoid myoepithelial cells, epithelial cells forming ducts or tubules, and the absence of nuclear atypia) and MRI (homogenous T2 hyperintensity, well-circumscribed borders, and solid contrast enhancement) all demonstrated PPVs of 95% or greater in patients with FNA diagnosis of PA.

CONCLUSIONS: PPV of a FNAB diagnosis of PA in the major salivary glands is high. Among patients with a FNAB diagnosis of PA, specific MRI characteristics also have a high PPV. The diagnostic accuracy of these studies in combination allows for the confident preoperative diagnosis of PA.