Diagnostic problems on frozen section examination of myometrial invasion in patients with endometrial carcinoma with special emphasis on the pitfalls of deep adenomyosis with carcinomatous involvement.

Frozen-section and paraffin section diagnoses were compared in 55 patients with Stage I endometrial adenocarcinoma. In 44 patients (80%), a corresponding depth of myometrial invasion and in 54 (98%) patients the same tumor grade were found. Regarding the depth of myometrial invasion and histologic grade, sensitivity, specificity, positive and negative predictive values were 70%, 86%, 73%, 83% and 92%, 100%, 100%, 94%, respectively. Concerning myometrial invasion 9% false-positivity and 10% false-negativity rates were noted. The histopathologic characteristics of false-positive and false-negative patients are emphasized because carcinomatous involvement of deeply situated adenomyosis and advanced grade tumors are the main diagnostic pitfalls. It is important for pathologists to be able to identify carcinomatous involvement of adenomyosis and adjacent foci of minimal myometrial invasion during frozen-section examination which can prevent aggressive surgery.