Accuracy of frozen section diagnosis at surgery in pre- malignant and malignant lesions of the endometrium.

Objective: The purpose of this study was to correlate the histological diagnosis made during intraoperative frozen section examination of hysterectomies with atypical hyperplasia or carcinoma, with the definitive paraffin section histology.

Study Design: Frozen section pathology results of patients with a preoperative biopsy showing atypical hyperplasia or endometrial carcinoma (87 patients) were compared retrospectively with paraffin section pathology findings. Those patients with curettage specimens showing atypical hyperplasia or curettings suspicious of endometrioid carcinoma had intraoperative frozen section to determine whether an invasive lesion was present and whether they required pelvic lymphadenectomy. The purpose of frozen section assessment in those patients who had a preoperative curettage specimen showing endometrial carcinoma was to identify poor prognostic pathological factors related to histological subtype, grade, depth of myometrial invasion and cervical involvement.

Results: The correlation between frozen sections and paraffin histology in patients with endometrial carcinoma was 98.6% (69/70) for histological sub-type and 84.3% (59/70) for grade of differentiation. Depth of myometrial invasion was accurately diagnosed in 94.3% (66/70) while cervical involvement was accurately assessed in 86.7% (52/60). Of the 37 patients with atypical hyperplasia or suspicious curettings on preoperative curettage who had intraoperative frozen section, 23 patients had invasive malignancy, which was confirmed in subsequent paraffin sections. Of the remaining 14 patients with a non-malignant frozen section diagnosis, 11 were confirmed with paraffin sections while three had a small well differentiated invasive lesion, two were FIGO Stage 1a and one had microscopic invasion into the myometrium.

Conclusion: Intraoperative frozen section is a useful procedure to identify poor prognostic pathological factors as well as to diagnose endometrial cancer in patients undergoing hysterectomy for a preoperative biopsy diagnosis of atypical hyperplasia.