Targeted sequencing with a customized panel to assess histological typing in endometrial carcinoma

The two most frequent types of endometrial cancer (EC) are endometrioid (EEC) and serous carcinomas (SC). Differential diagnosis between them is not always easy. A subset of endometrial cancers shows misleading microscopical features, which cause problems in differential diagnosis, and may be a good scenario for next-generation sequencing. Previous studies have assessed the usefulness of targeted sequencing with panels of generic cancer-associated genes in EC histological typing. Based on the analysis of TCGA (The Cancer Genome Atlas), EEC and SC have different mutational profiles. In this proof of principle study, we have performed targeted sequencing analysis with a customized panel, based on the TCGA mutational profile of EEC and SC, in a series of 24 tumors (16 EEC and 8 SC). Our panel comprised coding and non-coding sequences of the following genes: ABCC9, ARID1A, ARID5B, ATR, BCOR, CCND1, CDH19, CHD4, COL11A1, CSDE1, CSMD3, CTCF, CTNNB1, EP300, ERBB2, FBXW7, FGFR2, FOXA2, KLLN, KMT2B, KRAS, MAP3K4, MKI67, NRAS, PGAP3, PIK3CA, PIK3R1, PPP2R1A, PRPF18, PTEN, RPL22, SCARNA11, SIN3A, SMARCA4, SPOP, TAF1, TP53, TSPYL2, USP36, and WRAP53. Targeted sequencing validation by Sanger sequencing and immunohistochemistry was performed in a group of genes. POLE mutation status was assessed by Sanger sequencing. The most mutated genes were PTEN (93.7%), ARID1A (68.7%), PIK3CA (50%), and KMT2B (43.7%) for EEC, and TP53 (87.5%), PIK3CA (50%), and PPP2R1A (25%) for SC. Our panel allowed correct classification of all tumors in the two categories (EEC, SC). Coexistence of mutations in PTEN, ARID1A, and KMT2B was diagnostic of EEC. On the other hand, absence of PTEN, ARID1A, and KMT2B mutations in the presence of TP53 mutation was diagnostic of SC. This proof of concept study demonstrates the suitability of targeted sequencing with a customized endometrial cancer gene panel as an additional tool for confirming histological typing.