TCGA molecular classification in endometriosis-associated ovarian carcinomas: Novel data on clear cell carcinoma

Clear cell and endometrioid ovarian carcinomas (OCC and OEC, respectively) have a presumed origin in endometriosis and share molecular alterations with each other and with their endometrial counterparts. The Cancer Genome Atlas (TCGA)-based molecular classification stratifies endometrial carcinomas into four categories: POLE mutated (POLEmut), mismatch repair deficient (MMRd), p53 abnormal (p53abn) and no specific molecular profile (NSMP) with divergent prognoses. The subsequent studies are indicative that this TCGA classification has some value in OEC, but the knowledge related to OCC is limited.

Endometrial carcinoma molecular classification was evaluated and compared in a large series of OCCs (n = 115) and OECs (n = 158). POLE mutation analysis and tissue microarray-based immunohistochemistry for mismatch repair and p53 proteins were performed.

The distribution to the molecular groups was as follows: POLEmut 0.9%/3.2%, MMRd 3.5%/6.3%, p53abn 20%/30%, and NSMP 76%/60% in OCCs/OECs, respectively. The proportion of NSMP tumors was the largest in both histological types and significantly higher in OCC than OEC (p = 0.009). The molecular classification correlated significantly with DSS in both OCCs and OECs (p < 0.001 and p = 0.009, respectively), and with DFS in OCCs (p = 0.001). POLEmut and MMRd OCCs carried excellent prognosis, whereas MMRd OECs presented with poorer outcome. The p53abn group was associated with the poorest prognosis in both tumor types, particularly emphasized in OCCs.

TCGA molecular classification associated with patient outcome in both histotypes, and the difference in prognosis between the molecular groups was even more marked in OCC. The large amount of NSMP tumors highlights the need for further studies.