GSE118896
Translocation driven high expression of NOTCH2 in glomus tumors of the upper digestive tract
Glomus tumors (GT) are perivascular tumors mostly occurring in the distal extremities. Rare cases occur in the digestive tract and may be misdiagnosed with neuroendocrine or gastrointestinal stromal tumors. We aimed to specify the features of GT of the upper digestive tract.  We investigated two cases using whole exome sequencing (WES) and RNA-sequencing, and present clinical, histological, phenotypic and molecular features of 16 cases.  WES did not reveal any commonly involved cellular pathway. By contrast, RNA-sequencing disclosed a t(1:5)(p13;q32) translocation between MIR143HG and NOTCH2 in both cases. The deducted fusion protein sequence corresponded to the NOTCH2 intracellular domain known as NICD2, which acts as transcription factor.  These data were confirmed by high expression of the transcripts of genes targeted by NOTCH cellular pathway (HES and HEY gene families). In our retrospective multicentric series of 16 GT of upper digestive tract MIR143HG-NOTCH2 translocation was detected in 14 (88%) cases. By contrast, it was present in only 2/6 (33%) GT of the distal extremities.   Most digestive GT raised from the stomach (n=13), and the others from duodenal (2) or oesophagous (1). All digestive GT were positive for a-smooth muscle actin and transgelin, and negative for cytokeratin AE1/AE3, chromogranine, DOG1, KIT and S100. Most cases were positive for H-caldesmon (n=14) and/or for synaptophysin (n=10). Desmin, CD34 or CD56 were positive in only one case each. Nuclear expression of NOTCH2 was detected in the 14 cases containing the fusion transcripts.  The present study shows that MIR143HG-NOTCH2 translocation is present in most digestive GT. This fusion transcript is associated with activation of the NOTCH2 pathway and may drive tumor development. Detection of nuclear NOTCH2 expression may be helpful for diagnosis. Overall design: Examination of fusion transcript of 2 glomus tumors of the upper digestive tract