Proportion of Ovarian Cancers in Overall Ovarian Masses in Thailand

Background: The primary objective of this study was to assess the proportion of malignancies in ovarian masses during $1^{st}$ January 2002, to $31^{st}$ December 2011 at the Department of Obstetrics and Gynecology, King Chulalongkorn Memorial Hospital. A secondary objective was to evaluate associations with patients' clinical characteristics and ovarian malignancy proportion and subtypes. Materials and Methods: Retrospective descriptive study analyzed data of ovarian masses larger than 3 centimeters in maximal diameter, from the division of Gynecologic Cyto-Pathology at KCMH. SPSS software version 17 (SPSS, Inc, Chicago, IL, USA) was used. Results: A total number of 6,115 patients were included. Among the total ovarian masses studied, 13.7% were malignant. After the age of sixty, the proportion reached almost 40%. It was also above 20% in women younger than 20 years old. During premenarche period, proportion of ovarian malignancies was 50%. Only 1% of ovarian masses were found to be malignant during the pregnancy and post-partum periods. Parity decreased the probability of ovarian malignancy during postmenopausal years. Period of menopause did not have any impact on this probability. During the first two decades of life, germ cell malignancy dominated. As the age increased, the percentage of surface epithelial-stromal malignancy increased with a peak at the fifth decade. In contrast, malignant sex cord-stromal cell tumors occurred at a constant rate in each age group after the thirties. Conclusions: Proportion of ovarian cancers in each age group, menstrual and pregnancy status are similar. However there are differences in the distribution of ovarian subtypes especially for the surface epithelial-stromal category.