Supratentorial non-RELA, ZFTA-fused ependymomas: a comprehensive phenotype genotype correlation highlighting the number of zinc fingers in ZFTA-NCOA1/2 fusions

<jats:title>Abstract</jats:title><jats:p>The cIMPACT-NOW Update 7 has replaced the WHO nosology of “ependymoma, <jats:italic>RELA</jats:italic> fusion positive” by “Supratentorial-ependymoma, <jats:italic>C11orf95</jats:italic>-fusion positive”. This modification reinforces the idea that supratentorial-ependymomas exhibiting fusion that implicates the <jats:italic>C11orf95</jats:italic> (now called <jats:italic>ZFTA</jats:italic>) gene with or without the <jats:italic>RELA</jats:italic> gene, represent the same histomolecular entity. A hot off the press molecular study has identified distinct clusters of the DNA methylation class of <jats:italic>ZFTA</jats:italic> fusion-positive tumors. Interestingly, clusters 2 and 4 comprised tumors of different morphologies, with various <jats:italic>ZFTA</jats:italic> fusions without involvement of <jats:italic>RELA.</jats:italic> In this paper, we present a detailed series of thirteen cases of non-<jats:italic>RELA ZFTA</jats:italic>-fused supratentorial tumors with extensive clinical, radiological, histopathological, immunohistochemical, genetic and epigenetic (DNA methylation profiling) characterization. Contrary to the age of onset and MRI aspects similar to <jats:italic>RELA</jats:italic> fusion-positive EPN, we noted significant histopathological heterogeneity (pleomorphic xanthoastrocytoma-like, astroblastoma-like, ependymoma-like, and even sarcoma-like patterns) in this cohort. Immunophenotypically, these NFκB immunonegative tumors expressed GFAP variably, but EMA constantly and L1CAM frequently. Different gene partners were fused with <jats:italic>ZFTA</jats:italic>: <jats:italic>NCOA1/2</jats:italic>, <jats:italic>MAML2</jats:italic> and for the first time <jats:italic>MN1</jats:italic>. These tumors had epigenetic homologies within the DNA methylation class of ependymomas-RELA and were classified as satellite clusters 2 and 4. Cluster 2 (n = 9) corresponded to tumors with classic ependymal histological features (n = 4) but also had astroblastic features (n = 5). Various types of <jats:italic>ZFTA</jats:italic> fusions were associated with cluster 2, but as in the original report, <jats:italic>ZFTA:MAML2</jats:italic> fusion was frequent. Cluster 4 was enriched with sarcoma-like tumors. Moreover, we reported a novel anatomy of three <jats:italic>ZFTA:NCOA1/2</jats:italic> fusions with only 1 ZFTA zinc finger domain in the putative fusion protein, whereas all previously reported non-<jats:italic>RELA ZFTA</jats:italic> fusions have 4 ZFTA zinc fingers. All three cases presented a sarcoma-like morphology. This genotype/phenotype association requires further studies for confirmation. Our series is the first to extensively characterize this new subset of supratentorial <jats:italic>ZFTA</jats:italic>-fused ependymomas and highlights the usefulness of <jats:italic>ZFTA</jats:italic> FISH analysis to confirm the existence of a rearrangement without <jats:italic>RELA</jats:italic> abnormality.</jats:p>