Diagnostic accuracy of frozen section tests for surgical diseases.

Objective: To evaluate the accuracy of frozen section tests at different anatomical sites performed in an academic department of pathology.

Methods: We conducted a retrospective study from a computerized database of all frozen section tests. These diagnoses were compared to definite paraffin, used as controls. The tests were divided into three groups: inconclusive, consistent and inconsistent, the latter being subdivided into false positives and false negatives. The main indications for examinations and anatomical sites involved with diagnostic disagreements were also analyzed.

Results: Four hundred and thirty-three specimens were frozen tested, and the main indication was diagnostic (75.75%). In 404 tests (93.30%) diagnoses of biopsies in paraffin and frozen section were consistent. In 20 cases (4.62%) the results of frozen section biopsy were inconclusive and in 9 (2.08%) they were false negative. There were no false positive results. The most commonly assessed organ was the thyroid (25.64%). In the overall analysis, the body region most related with inconclusive diagnoses was the thyroid (seven cases) and in relation to specific sites it was the lungs/pleura/mediastinum (13.33%). Skin was the organ that showed more discordant diagnoses between frozen biopsies and paraffin.

Conclusion: The global accuracy of frozen section was 93.30%; for specific anatomical sites, diagnostic accuracy ranged from 86.67% to 100%.