Implication of genomic characterization in synchronous endometrial and ovarian cancers of endometrioid histology

Objectives Synchronous endometrial and ovarian carcinomas (SEOCs) present gynecologic oncologists with a challenging diagnostic puzzle: discriminating between double primary cancers and single primary cancer with metastasis. We aimed to determine the clonal relationship between simultaneously diagnosed endometrial and ovarian carcinomas. Methods Fourteen pairs of SEOCs of endometrioid type and two pairs of SEOCs with disparate histologic types (control for dual primary tumors) were subjected to massively parallel sequencing (MPS) and molecular inversion probe microarrays. Results Thirteen of the 14 pairs of SEOCs harbored somatic mutations shared by both uterine and ovarian lesions, indicative of clonality. High degree of chromosomal instability in the tumors from 10 patients who received adjuvant chemotherapy, of whom 9 had synchronous carcinomas with significantly overlapping copy number alterations (CNAs), suggestive of single primary tumors with metastasis. The clonal relationship determined by genomic analyses did not agree with clinicopathological criteria in 11 of 14 cases. Minimal CNAs were identified in both ovarian and endometrial carcinomas in 4 patients, who did not receive adjuvant chemotherapy and experienced no recurrent diseases. In contrast, two of the 10 patients with chromosomally unstable cancers developed recurrent tumors. Conclusion Our findings support a recent paradigm-shifting concept that most SEOCs originate from a single tumor. It also casts doubt on the clinicopathological criteria used to distinguish between dual primary tumors and single primary tumor with metastasis. Testing of CNAs on SEOCs may help determining the need of adjuvant therapy.