Micropapillary and cribriform patterns in ovarian serous tumors of low malignant potential: a study of 99 advanced stage cases.

Recently some investigators have proposed abandoning the term ovarian serous tumor of low malignant potential (SLMP) and dividing the tumors in this category into two new groups, micropapillary serous carcinoma and atypical proliferative serous tumor, based on the presence or absence of marked epithelial proliferation with a micropapillary or cribriform pattern (MP/CP). We reviewed 99 cases of advanced stage SLMP (FIGO stages II and III) to determine whether the presence or absence of MP/CP predicts the clinical course, thus justifying the proposed change in terminology. Eighteen cases of MP/CP and 81 cases of typical SLMP were identified. The patients with MP/CP ranged from 23 to 59 years of age at the time of diagnosis (median 35 years), whereas those with typical SLMP were 17 to 67 years old (median 38 years). Bilateral ovarian involvement by SLMP was more frequent in the MP/CP cases, 13 of 18 (72%), as compared with the cases with typical SLMP, 46 of 81 (57%). There was a trend toward a greater frequency of invasive implants in MP/CP cases, 3 of 18 (17%) MP/CP versus 5 of 81 (6%) typical. The mean follow-up period was 125 months for MP/CP patients and 132 months for the typical group. Differences in the frequency of recurrence and the progression-free survival between the groups were found to be significant. Fourteen (78%) of the MP/CP patients experienced either progression or recurrence of disease, whereas 25 (31%) of the typical SLMP patients had a recurrence (p = 0.001). The progression-free survival ranged from 3 to 208 months for MP/CP patients versus 15 to 233 months for typical SLMP patients (p <0.0001). The majority of the recurrences in both groups were low-grade serous carcinoma, 11 of 14 (79%) patients with progression/recurrence in the MP/CP group and 17 of 25 (68%) patients with recurrence in the typical group. The overall survival of the patients in the two groups, however, was not significantly different. Five (28%) MP/CP patients and 12 (15%) patients with typical SLMP died of disease (p = 0.11). All 17 of these patients developed serous carcinoma and died secondary to tumor progression. Four of eight (50%) patients with invasive implants and 13 of 91 (14%) patients with noninvasive implants died of disease. Our findings of more frequent bilateral ovarian involvement, more frequent recurrence with a shorter progression-free interval, and the trend toward a more frequent association with invasive implants support the contention that MP/CP SLMP are a distinct subgroup of serous tumors. However, the overall survival of patients with MP/CP SLMP is similar to that of patients with typical SLMP and justifies the retention of tumors with MP/CP within the LMP category. Additionally, our long-term follow-up of patients with typical SLMP indicates that a number of these tumors do not follow a benign course and supports their continued designation as borderline neoplasms.