Abstract 3716: The origin of metastatic ovarian tumors: A national population-based analysis

Abstract Objective: A significant part of ovarian malignancies are metastatic tumors with a wide variety in site of origin. Differentiating between a primary and metastatic malignancy of the ovaries can be difficult, especially in case of mucinous carcinomas, and misdiagnosis might have considerable impact on both treatment and prognosis. To further examine the origin of metastatic tumors in the ovary, we performed a large scale, nationwide search for metastatic ovarian malignancies in the Dutch Pathology Registry (PALGA). Materials and methods: All pathology reports concerning metastatic ovarian carcinomas and associated primary tumors in the Netherlands from 2000-2010 were collected. Age, year of diagnosis, tumor type, location of the primary tumor and laterality of the ovarian tumor were extracted from the database. Tumors without a proven primary tumor were excluded. The Chi-square test was used to compare multiple nominal variables. Results: 2,312 patients were identified. The most common primary sites were colon (33.2%), endometrium (17.1%), breast (14.3%), appendix (7.3%) and stomach (4.5%). Bilateral tumors were the most frequent mode of presentation (46.3%) followed by right (26.7%) and left side metastases (19.8%). In 7.2% of cases, laterality was unknown. Mucinous carcinomas were the most common histological type (46.7%), followed by signet-ring cell carcinomas (7.9%) and endometrioid carcinomas (7.7%). Of colorectal tumors, only 40.2% metastasized bilaterally, compared to 64% of breast, 63% of gastric and 59% of appendix tumors. Left sided ovarian tumors originated more often from the left colon than the right colon (69.4%, p<0.0001). Right sided ovarian tumors did not originate more often from the right side of the colon than from the left side. Appendiceal primary tumors did give rise to more right sided ovarian metastases (71.6%, p = 0.016). Conclusion: The most common histological tumor type in metastatic ovarian carcinomas is mucinous carcinoma. The colon is the most frequent primary site of metastatic malignancies to the ovaries, followed by endometrium, breast, appendix and stomach. Breast, stomach and appendix tumors metastasized mostly bilateral, whereas colorectal tumors metastasized mostly unilateral and ipsilateral. The mechanisms underlying these preferred sites for metastasis or laterality are still unclear. Citation Format: Michiel Simons, Jolien Bruls, Lucy Overbeek, Johan Bulten, Leon Massuger, Iris Nagtegaal. The origin of metastatic ovarian tumors: A national population-based analysis. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3716. doi:10.1158/1538-7445.AM2015-3716