The accuracy of frozen section diagnosis of parotid lesions.

A study to assess the accuracy of frozen section diagnosis for parotid lesions was conducted. All parotid cases from the surgical pathology files at the Toronto General Hospital (TGH) for the period 1978-83 were reviewed. A total of 131 specimens were obtained. Frozen sections were requested for 110 of these specimens, 90 of which were benign and 20 of which were malignant. The pathology reports, patient charts, and histology slides were examined. Errors were analyzed as to type. The frozen section accuracy for providing a specific histopathologic diagnosis was 94%. When considering only the ability to distinguish benign from malignant lesions, the accuracy improved to 97%. The deferral rate was 1.8% (two patients). In five instances, the diagnosis obtained by frozen section directly altered the surgical management. No unnecessary surgery was performed based on a frozen section result. In no case was a frozen section diagnosis of malignancy changed to a benign diagnosis upon paraffin section review. The medical chart review of the 21 patients where frozen section was not requested revealed two patients for whom the knowledge of a specific diagnosis at surgery may have altered the patient management. The TGH experience compares favorably with results obtained in three similar, recently published studies (UCLA, 1979; Stanford, 1983; Seattle, 1984). Frozen section diagnosis of parotid lesions, in our hands, is a safe, accurate and useful diagnostic tool.