Pleomorphic adenoma: A diagnostic pitfall in the diagnosis of salivary gland lesions on FNAC: Case reports with review of the literature

Fine needle aspiration cytology (FNAC) is commonly being used with increasing frequency for the pre-operative evaluation of salivary gland lesions. However, it has areas of considerable interpretational difficulties. The most frequent problems involve variations in the expected cytology of pleomorphic adenoma (PA). Salivary gland FNACs performed at Pt. JNM Medical College, Raipur, Chhattisgarh, during July 2006 to June 2007 were reviewed, and we report four cases of interesting diagnostic dilemma. As PA is the most common salivary gland neoplasm, it should always be considered and ruled out as the first differential in the diagnosis of salivary gland FNACs. In order to avoid diagnostic pitfalls, we emphasize a diagnostic approach based on the mandatory presence of all three elements of PA, i.e. 3-dimensional cohesive clusters of ductal cells, background of singly lying plasmacytoid myoepithelial cells and dense fibrillary brightly metachromatic stroma with partially obscured entrapped myoepithelial cells. To document the same, we advocate liberal use of repeat aspirations with multiple sampling performed from different parts of the tumor. Some differential diagnostic problems, e.g. carcinoma ex PA, may still however remain insolvable by cytologic means.