Diagnostic accuracy and pitfalls of preoperative fine needle aspiration cytology in salivary gland lesions

Abstract

Purpose: Evaluation of diagnostic accuracy of preoperative fine needle aspiration cytology (FNAC) in salivary gland lesions.

Patients and methods: This is a retrospective study of 82 patients presented at NCI, Cairo University with salivary gland lesion who underwent preoperative FNAC diagnosis with subsequent excision and histopathologic assessment. Cytology results were classified as negative, positive, suspicious for cancer and inadequate. The definitive histopathologic report according to WHO Histological typing was the gold standard diagnosis against which FNAC was compared.

Results: Our study included 82 patients who underwent preoperative FNAC of major salivary glands with subsequent surgical excision. Male to female ratio was 1.4: 1. The median age was 42 years. Parotid gland was involved in (68.3%), submandibular in (28%) and submental gland in (3.7%). Forty cases (48.8%) were cytologically diagnosed as benign lesions, 26 (31.7%) were malignant and 10 (12.2%) were suspicious. Cytological findings were nondiagnostic in 6 (7.3%). The most common benign cytologic diagnosis was pleomorphic adenoma; 16 out of 40 cases (40%), while the most common malignant tumor was carcinoma; 22 out of 26 cases (84.6%). Cytologic diagnoses were compared with histopathologic ones and were true-negative in 37 (92.5%), true-positive in 33 (91.6%), false-negative in 3 (8.3%) and false-positive in 3 (7.5%) cases regarding detection of malignant tumors. The cytologic diagnosis achieved a sensitivity of 91.7%; a specificity of 92.5%, PPV 91.6%, NPV 92.5% and diagnostic accuracy 92%. The rates of agreement of histopathologic type for benign and malignant tumors were 89.2% and 91%, respectively.

Conclusion: The sensitivity, specificity and diagnostic accuracy of FNAC were 91.7%, 92.5% and 92%, respectively. Attention to subtle morphologic changes, pitfalls and limitations are important to increase diagnostic accuracy. Multidirectional aspiration is preferred to avoid selective sampling. Re-aspiration of solid portion after cyst fluid aspiration is necessary to decrease the rate of inadequacy.

Key words: FNAC - Salivary gland lesions - Accuracy - Pitfalls.