Prognostic Significance of Stromal Microinvasion in the Intestinal Type of Ovarian Mucinous Adenocarcinoma

The purpose of this study was to assess clinical outcomes with respect to the extent of stromal invasion in patients with stage I ovarian mucinous adenocarcinoma (MAC) of the intestinal type. We retrospectively reviewed the medical records and pathologic slides of 113 patients with stage I ovarian MACs who were treated at the Asan Medical Center from January 1994 to July 2009. According to the recent histopathologic criteria, MACs were classified into 3 groups: intraepithelial carcinoma without invasion (IEC), intraepithelial carcinoma with microinvasion (IECMI), and mucinous adenocarcinoma with extensive invasion (MACEI). Stromal invasion was confined to the tumors showing severe cytologic atypia in the invasive foci. Therefore, cases showing mucin granulomas composed only of macrophages without malignant cells were excluded from the definition of invasion. Of the 113 patients, 54 (47.8%) had IEC, 15 (13.3%) had IECMI, and 44 (38.9%) had MACEI. There were no differences among groups in age, menopausal status, CA-125 level, surgical procedures, stage, capsular and lymphovascular space invasion. The 5-year disease-free-survival rates in the IEC, IECMI, and MACEI groups were 97.7%, 77.3%, and 79.9%, respectively (IEC vs IECMI, P = 0.004; IEC vs MACEI, P = 0.012; IECMI vs MACEI, P = 0.555). Prognosis was significantly poorer for patients with IECMI than for those with IEC, but not different between patients with IECMI and MACEI. Stromal microinvasion in ovarian MAC is a significant prognostic factor. Therefore, diligent search for “stromal microinvasion” with adequate sampling of tumor tissue are important at the time of histopathologic diagnosis, and patients with IECMI should no longer be treated identically to those with IEC.