Diagnostic difficulties in fine needle aspiration of benign salivary glandular lesions

Abstract

Background: The diagnostic accuracy of fine needle aspiration cytology (FNAC) of salivary lesions is relatively high, but cytologic interpretation might be confusing if the sample is lacking typical cytologic features.

Methods: There were 77 cases of benign salivary lesions, consisting of pleomorphic adenoma (PA) in 61 cases, Warthin's tumor (WT) in 12 cases, and other benign lesions in 4 cases. The causes of the discrepancies between the FNAC and the histologic diagnoses were evaluated.

Results: Major discrepancies were noted in 4 of the 61 PA cases, and in 1 of 12 WT cases. The causes of the major discrepancies were a mislabeled site in 1 PA and 1 WT case, and an interpretation error in 3 PA cases. Minor discrepancies were more common in the WT cases (7 of 12 cases) than in the PA cases (11 of 61 cases). The causes of the minor discrepancies were a mislabeled site in 1 PA and 1 WT case, an inadequate sample in 7 PA and 2 WT cases, a lack of typical cytomorphology in 2 PA and 2 WT cases, and an interpretation error in 1 PA and 2 WT cases.

Conclusions: To increase the diagnostic accuracy in the benign salivary lesions, recognition of both characteristic and less typical cytomorphology is needed.

Keywords: Benign lesion; Biopsy, fine-needle; Salivary glands.

Fig. 1

Cytologic and histologic findings of pleomorphic adenoma case misdiagnosed as mucoepidermoid carcinoma. The fine needle aspiration cytology smear shows a few cellular clusters with squamoid features (A), and histologically squamous metaplasia and microcystic changes are observed (B).

Fig. 2

Cytologic findings of pleomorphic adenoma cases misdiagnosed as an inflammatory condition. The fine needle aspiration cytology smear displays low cellularity with a lack of three cellular components such as epithelial, myoepithelial and stromal origin (A), and the nuclear debris in the necrotic background that are misinterpreted as inflammatory cells (B).

Fig. 3

Cytologic findings of the Warthin's tumor cases showing diagnostic discrepancies. The typical cytologic features of Warthin's tumor consist of oncocytic cell clusters and mature lymphocytes in the necrotic background (A). A case, diagnosed as simply benign, shows degenerated or squamoid cells mixed with inflammatory cells instead of oncocytic cell clusters (B). Another Warthin's tumor case with cystic change reveals cell debris in the necrotic background (C), and scanty spindled or squamoid cells mixed with cell debris (D).