In most diagnostic laboratories, targeted next-generation sequencing (NGS) is currently the default assay for the detection of somatic variants in solid as well as haematological tumours. Independent of the method, the final outcome is a list of variants that differ from the human genome reference sequence of which some may relate to the establishment of the tumour in the patient. A critical point towards a uniform patient management is the assignment of the biological contribution of each variant to the malignancy and its subsequent clinical impact in a specific malignancy. These so-called biological and clinical classifications of somatic variants are currently not standardized and are vastly dependent on the subjective analysis of each laboratory. This subjectivity can thus result in a different classification and subsequent clinical interpretation of the same variant. Therefore, the ComPerMed panel of Belgian experts in cancer diagnostics set up a working group with the goal to harmonize the biological classification and clinical interpretation of somatic variants detected by NGS. This effort resulted in the establishment of a uniform, two-level classification workflow system that should enable high consistency in diagnosis, prognosis, treatment and follow-up of cancer patients. Variants are first classified into a tumour-independent biological five class system and subsequently in a four tier ACMG clinical classification. Here, we describe the ComPerMed workflow in detail including examples for each step of the pipeline. Moreover, this workflow can be implemented in variant classification software tools enabling automatic reporting of NGS data, independent of panel, method or analysis software.

The TLX1 transcription factor is critically involved in the multi-step pathogenesis of T-cell acute lymphoblastic leukemia (T-ALL) and often cooperates with NOTCH1 activation during malignant T-cell transformation. However, the exact molecular mechanism by which these T-cell specific oncogenes cooperate during transformation remains to be established. Here, we used chromatin immunoprecipitation followed by sequencing to establish the genome-wide binding pattern of TLX1 in human T-ALL. This integrative genomics approach showed that ectopic TLX1 expression drives repression of T cell-specific enhancers and mediates an unexpected transcriptional antagonism with NOTCH1 at critical target genes, including IL7R and NOTCH3. These phenomena coordinately trigger a TLX1-driven pre-leukemic phenotype in human thymic precursor cells, reminiscent of the thymus regression observed in murine TLX1 tumor models, and create a strong genetic pressure for acquiring activating NOTCH1 mutations as a prerequisite for full leukemic transformation. In conclusion, our results uncover a functional antagonism between cooperative oncogenes during the earliest phases of tumor development and provide novel insights in the multi-step pathogenesis of TLX1-driven human leukemia.

Ovarian cancer is the most lethal gynecologic malignancy, mainly due to late-stage diagnosis, frequent recurrences, and eventually therapy resistance. To identify potentially actionable genetic variants, sequencing data of 351 Belgian ovarian cancer patients were retrospectively captured from electronic health records. The cohort included 286 (81%) patients with high-grade serous ovarian cancer, 17 (5%) with low-grade serous ovarian cancer, and 48 (14%) with other histotypes. Firstly, an overview of the prevalence and spectrum of the BRCA1/2 variants highlighted germline variants in 4% (11/250) and somatic variants in 11% (37/348) of patients. Secondly, application of a multi-gene panel in 168 tumors revealed a total of 214 variants in 28 genes beyond BRCA1/2 with a median of 1 (IQR, 1–2) genetic variant per patient. The ten most often altered genes were (in descending order): TP53, BRCA1, PIK3CA, BRCA2, KRAS, ERBB2 (HER2), TERT promotor, RB1, PIK3R1 and PTEN. Of note, the genetic landscape vastly differed between the studied histotypes. Finally, using ESCAT the clinical evidence of utility for every genetic variant was scored. Only BRCA1/2 pathogenic variants were classified as tier-I. Nearly all patients (151/168; 90%) had an ESCAT tier-II variant, most frequently in TP53 (74%), PIK3CA (9%) and KRAS (7%). In conclusion, our findings imply that although only a small proportion of genetic variants currently have direct impact on ovarian cancer treatment decisions, other variants could help to identify novel (personalized) treatment options to address the poor prognosis of ovarian cancer, particularly in rare histotypes.

Preoperative imaging and histopathology, immunohistochemistry and molecular analysis after resection of 2 hepatocellular adenomas (HCAs) (20 and 2cm) in a 53-year-old female patient were performed. On imaging, the large lesion resembled a myxoid HCA, while the small lesion resembled a more conventional HCA with a small myxoid/fluid area. On microscopy, the large lesion showed cords and nests of hepatocytes embedded in abundant myxoid matrix, while the small lesion resembled a conventional HCA with small foci of myxoid change and serosities; both consistent with a myxoid HCA. Immunophenotyping and molecular subtyping excluded inflammatory HCA, CTNNB1 mutated HCA and sonic hedgehog HCA, and was consistent with HNF1A mutated HCA. The myxoid change as well as the serosities may allow imaging diagnosis of myxoid HCA. As fluid vacuoles can also be present in ASS1+HCA, sonic hedgehog HCA has to be considered in the differential diagnosis.