Search

High-grade endometrial stromal sarcomas (HGESSs) are more aggressive and have higher rates of resistance to endocrine therapy than low-grade endometrial stromal sarcomas (LGESSs). The pathogenesis of hormonal resistance in these lesions has yet to be defined. Here we sought to histologically and genetically characterize 3 LGESSs and their recurrences that underwent histologic high-grade transformation following endocrine therapy. For this, DNA from primary tumors and select subsequent recurrences were subject to massively parallel sequencing targeting 468 cancer-related genes. Somatic mutation analyses were performed using validated bioinformatics methods. In addition, RNA from each case was evaluated for the presence of gene fusions using targeted RNA-sequencing. All patients initially presented with LGESS, developed HGESS recurrences, and received at least 2 lines of hormonal suppressive therapy. Gene fusions classically described as associated with LGESS were identified in all 3 cases, including JAZF1-PHF1, EPC1-PHF1and JAZF1-SUZ12fusions for Cases 1, 2 and 3, respectively. Targeted sequencing analysis revealed that none of the primary LGESS, however the HGESS recurrences of Cases 1 and 3, and the LGESS and HGESS recurrences of Case 2 post endocrine treatment harbored ESR1p.Y537S hotspot mutations. These ESR1ligand-binding domain mutations have been found as a mechanism of acquired endocrine resistance in breast cancer. Also, a reduction in estrogen receptor (ER) expression was observed in recurrences. Our findings suggest that the ESR1p.Y537S hotspot mutation in LGESS with histologic high-grade transformation may be associated with endocrine resistance in these lesions. Furthermore, our data suggest that genetic analyses may be performed in recurrent LGESS following hormonal therapy, development of high-grade morphology, and/or altered/diminished ER expression.

Uterine perivascular epithelioid cell tumor (PEComa) is a rare mesenchymal neoplasm that occasionally shares morphologic and immunohistochemical overlap with low- and high-grade endometrial stromal sarcoma (LGESS and HGESS). In this study, we sought to characterize the clinical, morphologic, genetic, and epigenetic features of five uterine sarcomas that display histologic features of LGESS, HGESS, and PEComa. All tumors demonstrated epithelioid cells often associated with a low-grade spindled component resembling LGESS, with both regions expressing CD10, ER, PR, variable HMB45, and Melan-A immunoreactivity, and strong cathepsin K and pS6 expression. Targeted massively parallel sequencing analysis revealed the presence of somatic TSC2mutations in all five cases, of which four harbored concurrent or consecutive JAZF1-SUZ12gene fusions. Unsupervised hierarchical clustering analysis of methylation profiles of TSC2-mutant uterine sarcomas (n= 4), LGESS (n= 10), and HGESS (n= 12) demonstrated two clusters consisting of (1) all LGESS and TSC2-mutant uterine sarcomas and (2) all HGESS. KEGG pathway analysis detected methylation differences in genes involved in PI3K/AKT, calcium, and Rap1 signaling. TSC2-mutant uterine sarcomas were responsive to hormone suppression, and mTOR inhibition demonstrated clinical benefit in four patients with these neoplasms. Our results suggest that these tumors represent histologically distinctive LGESS with TSC2mutations. TSC2mutations and JAZF1-SUZ12fusion may help diagnose these tumors and possibly direct effective treatment.

Uterine perivascular epithelioid cell tumor (PEComa) is a rare mesenchymal neoplasm that occasionally shares morphologic and immunohistochemical overlap with low- and high-grade endometrial stromal sarcoma (LGESS and HGESS). In this study, we sought to characterize the clinical, morphologic, genetic, and epigenetic features of five uterine sarcomas that display histologic features of LGESS, HGESS, and PEComa. All tumors demonstrated epithelioid cells often associated with a low-grade spindled component resembling LGESS, with both regions expressing CD10, ER, PR, variable HMB45, and Melan-A immunoreactivity, and strong cathepsin K and pS6 expression. Targeted massively parallel sequencing analysis revealed the presence of somatic TSC2mutations in all five cases, of which four harbored concurrent or consecutive JAZF1-SUZ12gene fusions. Unsupervised hierarchical clustering analysis of methylation profiles of TSC2-mutant uterine sarcomas (n= 4), LGESS (n= 10), and HGESS (n= 12) demonstrated two clusters consisting of (1) all LGESS and TSC2-mutant uterine sarcomas and (2) all HGESS. KEGG pathway analysis detected methylation differences in genes involved in PI3K/AKT, calcium, and Rap1 signaling. TSC2-mutant uterine sarcomas were responsive to hormone suppression, and mTOR inhibition demonstrated clinical benefit in four patients with these neoplasms. Our results suggest that these tumors represent histologically distinctive LGESS with TSC2mutations. TSC2mutations and JAZF1-SUZ12fusion may help diagnose these tumors and possibly direct effective treatment.

Anti-HER2 targeted therapies have recently demonstrated clinical activity in the treatment of high-grade endometrial carcinomas (EC), particularly serous carcinomas with HER2amplification and/or overexpression. Intratumor heterogeneity of HER2amplification, or HER2genetic intratumor heterogeneity (G-ITH), has been associated with resistance to anti-HER2 therapies in breast and gastroesophageal cancers, however, its clinical relevance in EC is unknown. To characterize HER2G-ITH in EC, archival specimens from a clinically annotated cohort of 57 ECs treated with trastuzumab or trastuzumab-emtansine in the recurrent (n=38) or adjuvant (n=19) setting were subjected to central pathology review, HER2 assessment by immunohistochemistry (IHC) and fluorescence in-situhybridization (FISH), and next-generation sequencing (NGS). HER2G-ITH, defined as HER2amplification in 5%-50% of tumor cells examined by FISH, was identified in 36% (19/53) of ECs and was associated with lower HER2copy number and levels of protein expression. HER2 IHC revealed spatially distinct areas of strong expression juxtaposed with areas of low/absent expression in tumors with the “cluster” pattern of G-ITH, while the “mosaic” pattern was typically associated with a diffuse admixture of cells with variable levels of HER2 expression. HER2G-ITH was frequently observed in cases with IHC/FISH or FISH/NGS discrepancies and/or with an equivocal/negative FISH result (9/13, 69%). While the objective response rate to anti-HER2 therapy in recurrent ECs was 52% (13/25) for tumors lacking HER2G-ITH, none (0%, 0/10) of the patients with HER2G-ITH achieved a complete or partial response (p=0.005). HER2G-ITH was significantly associated with worse progression-free survival (HR 2.88 (95% CI 1.33-6.27), p=0.005), but not overall survival. HER2 IHC score, HER2/CEP17ratio, HER2copy number, histologic subtype, and other genetic alterations, including PIK3CAhotspot mutations, were not significantly associated with therapeutic response or survival outcomes. Treatment responses were not restricted to serous carcinomas, supporting consideration of anti-HER2 therapy in patients with HER2-positive high-grade ECs of non-serous histology. Our results demonstrate that HER2G-ITH is an important determinant of response to trastuzumab and trastuzumab-emtansine in EC, providing a rationale for development of novel therapeutic strategies to target HER2-non-amplified resistant tumor subpopulations, such as HER2 antibody drug conjugates with bystander effects.