After Scully divided the primary ovarian epithelial tumors into benign, borderline and
malignant varieties, it has been repeatedly emphasized that there are appreciable
differences in terms of prognosis in each group. However there may be individual
difference among examiners when the pathological diagnosis is made on the basis of
complex interpretation of the nuclear pleomorphism, mode of proliferation, frequency of
mitosis and the presence of stromal invasion. In this study histological grading was
made according to the frequency of mitosis, the most reliable index for the rate of
cellular proliferation, in 98 mucinous ovarian tumors. Of the 98 subjects 80 cases
belonged to the grade I (0∼1 mitosis/HPF), and the grade Ⅱ(2∼3/ HPF), Ⅲ(4∼5/HPF)
and Ⅳ(>5/HPF) tumors were seen in 11, 5 and 2 cases respectively. The degree of
nuclear pleomorphism and the mode of cellular proliferation, such as the frequency and
degree of papillary growth and secondary gland formation, corresponded well to the
grades of tumors. Among the 98 mucinous tumors, seven cases (7.1%) showing stromal
invasion were classified as malignant, irrespective of histologic grades, and all the grade
I tumors but those with stromal invasion was grouped into benign, which comprised
80.6%. The remaining tumors were categorized into borderline malignancy which
comprised 12.3% of all. The grade Ⅳ tumors showed smaller size and less
multilocularity than the lower grade ones, suggesting that the higher-grade tumors tend
to grow as solid mass rather than cystic locales. The short symptom-duration as well
as the bilateral involvement were more likely of higher grade tumors. It was emphasized
that one must pay regard to the frequency of mitosis when primary mucinous ovarian
tumors were dealt with.
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