Fine-needle aspiration biopsy of parotid lesions: comparison with frozen section

Opinions vary as to the necessity for fine-needle aspiration biopsy (FNAB) in parotid tumours. The present study reflects the experience gained over a 12-year period and shows the accuracy of a diagnostic FNAB, and improved results with experience.

Between 1983 and 1995, 201 parotid lesions were excised by one surgeon(AGP) and a prospective database was established. Fine-needle aspiration biopsy was performed prior to surgery in 195 lesions and frozen section was performed in 159 lesions.

The FNAB was diagnostic in 129 (66%) specimens and its sensitivity for malignancy was 90% and specificity was 100% (excluding non-diagnostic FNAB, where there was insufficient cellular material for reliable diagnosis or where specific tissue diagnosis could not be given). The positive predictive value was 100% and the negative predictive value was 98%. Of interest, the positive predictive value of diagnostic FNAB for pleomorphic adenomas was 99%. A specific tumour diagnosis could not be made on the FNAB sample in 37 specimens; 11 of these lesions were histologically confirmed as malignant after excision. Frozen section was diagnostic in 144 specimens (91%). Its sensitivity for malignancy was 96% and specificity was 99%. The positive predictive value was 96% and negative predictive value 99%. A specific tumour diagnosis could not be made on frozen section in 15 specimens including six cases in which malignancy was finally reported. The positive predictive value of diagnostic frozen section for pleomorphic adenomas was 99%.

A diagnostic FNAB is an accurate and useful tool in the management of parotid lesions. An FNAB diagnosis of pleomorphic adenoma obviates the need for frozen section. The performance of FNAB in parotid tumours does not in any way preclude the necessity of surgical removal of such lesions except in exceptional circumstances.