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%.