Frozen Section as a Rapid and Accurate Method for Diagnosing Acute Invasive Fungal Rhinosinusitis

Objective: Identify methods to improve the frozen-section diagnosis of acute invasive fungal rhinosinusitis. Study Design: Biopsies with frozen section for suspected acute invasive fungal rhinosinusitis were reviewed to identify causes for missed diagnoses and evaluate methods for potential improvement. Setting: All aspects of the study were performed at the Penn State Milton S. Hershey Medical Center. Subjects and Methods: All frozen sections performed for suspected acute invasive fungal rhinosinusitis between 2006 through 2017 were reviewed with their diagnoses compared to the final diagnoses. Sensitivity and specificity were determined for each biopsy specimen to evaluate the diagnostic method and for each patient for its effectiveness on outcome. Causes for frozen-section failures in diagnosis were identified. A periodic acid–Schiff stain for fungus (PASF) was modified for use on frozen tissue (PASF-fs) and applied both retrospectively and prospectively to frozen sections to determine its ability to identify undetected fungus and improve diagnostic sensitivity. Results: Of 63 biopsies positive for acute invasive fungal rhinosinusitis, 51 were diagnosed on frozen section, while 61 were identified by including the novel PASF-fs stain, reducing the failure rate from 19% to 3%. Of 41 cases that were positive, 34 were diagnosed on frozen section. Of the 7 that were not, 5 were identified by including the PASF-fs, reducing the failure rate from 17% to 5%. Conclusions: Frozen section interpretation of biopsies for suspected acute invasive fungal rhinosinusitis using a PASF-fs stain should enable a rapid and accurate diagnosis with improved outcomes by shortening the time to surgery.