No abstract

Mixed endometrial carcinomas are defined as a combination of 2 or more distinct histologic subtypes, one of which must be a type II tumor comprising at least 5% of the tumor volume. The oncogenesis of these tumors remains unclear, particularly in light of the increasingly appreciated morphologic overlap among subtypes, as well as evolving molecular data. We evaluated 8 cases of mixed endometrial carcinoma, including 4 endometrioid (EC)/serous (SC), 1 SC/clear cell (CC), and 3 EC/CC cases, to study the underlying molecular features and oncogenic mechanisms at play. Each component was analyzed by a targeted next-generation sequencing assay. All tumors shared mutations in both components. In 6 cases, one component showed additional mutations. Two EC/SC cases showed shared mutations and mutations unique to each component. When present, unique mutations were typically seen in the SC component, including variants in POLE and TP53, as well as potentially targetable genes DDR2, MAP2K1, and CCNE1. In EC/SC tumors, ERBB2 abnormalities were seen in 2 cases. EC/CC cases showed FGFR2 activating mutations in the EC component only. No fusion drivers were identified. Our data suggest that the majority of these tumors begin as a single clone and diverge along 2 pathways: (1) tumor progression, with one component showing additional mutations, and (2) tumor divergence, in which tumor components have both shared mutations and mutations unique to each component. In addition, the findings suggest a component of morphologic mimicry in these tumors. Our findings are clinically relevant since targetable mutations may be present in only one component of mixed tumors.

Background Endoscopic ultrasound–guided fine needle aspiration (EUS‐FNA) is a sensitive and specific tool in the risk stratification of pancreatic lesions, including cysts. The sensitivity and specificity of EUS‐FNA has been shown to improve when cytology is combined with next‐generation sequencing (NGS). Ideally, fresh cyst fluid is used for NGS. In this pilot study, we explore the possibility of sequencing DNA derived from residual alcohol‐fixed pancreatic aspirates. Methods Residual cytologic fixatives (n = 42) from 39 patients who underwent EUS‐FNA for pancreatic lesions were collected along with demographics, imaging, and laboratory studies. Samples were designated as nonneoplastic/nonmucinous benign (NB), mucinous cyst (MC), pancreatic ductal adenocarcinoma (PDAC), or well‐differentiated neuroendocrine tumor (NET) on the basis of cytopathologic evaluation and sequenced on the Oncomine platform (ThermoFisher Scientific, Waltham, Massachusetts). Results Ten of 14 (71.4%) MCs exhibited clinically significant variants, including KRAS, GNAS, and TP53. Ten of 15 (66.7%) PDACs had KRAS alterations, and 9 of 15 (60%) showed variants in TP53. No variants were detected in any NETs. Only 1 of 9 (11.1%) NB aspirates showed variants in KRAS and MAP2K. Sequencing of formalin‐fixed, paraffin‐embedded tissue revealed variants identical to those detected in fixative‐derived DNA in 4 of 5 cases (80%). Conclusion Residual DNA from alcohol‐fixed aspirates are an underutilized source for NGS. Sequencing residual fixative‐derived DNA has the potential to be integrated into the workup of pancreatic aspirates, possibly impacting management.

Low-grade, low-stage endometrioid carcinomas (LGLS EC) demonstrate 5-yr survival rates up to 95%. However, a small subset of these tumors recur, and little is known about prognostic markers or established mutation profiles associated with recurrence. The goal of the current study was to identify the molecular profiles of the primary carcinomas and the genomic differences between primary tumors and subsequent recurrences. Four cases of LGLS EC with recurrence and 8 cases without recurrence were evaluated via whole-exome sequencing. Three of the 4 recurrent tumors were evaluated via Oncomine Comprehensive Assay. The resulting molecular profiles of the primary and recurrent tumors were compared. Two of the 3 recurrent cases showed additional mutations in the recurrence. One recurrent tumor included an additional TP53 mutation and the other recurrent tumor showed POLE and DDR2 kinase gene mutation. The POLE mutation occurred outside the exonuclease domain. PIK3CA mutations were detected in 4 of 4 primary LGLS EC with recurrence and in 3 of 8 disease-free cases. LGLS EC with recurrence showed higher MSIsensor scores compared with LGLS without recurrence. The level of copy number gains in LGLS EC with recurrence was larger than LGLS EC without recurrence. This pilot study showed 1 of 3 recurrent cases gained a mutation associated with genetic instability (TP53) and 1 of them also acquired a mutation in the DDR2 kinase, a potential therapeutic target. We also noted a higher level of copy number gains, MSIsensor scores and PIK3CA mutations in the primary tumors that later recurred.