A Molecular Reappraisal of Glomus Tumors and Related Pericytic Neoplasms With Emphasis on NOTCH-gene Fusions

This study aimed to investigate the prevalence and specificity of NOTCH-gene fusions in a large group of GT and correlate with clinical features. BRAF-VE1 and PDGFRB immunoexpression was also investigated in this cohort. A total of 93 GT and 43 other pericytic lesions (11 MP, 13 MF, and 19 AL) were selected. All cases were tested by fluorescence in situ hybridization for NOTCH1-4 and MIR143 gene abnormalities and 6 cases were investigated by targeted RNA-sequencing. Fluorescence in situ hybridization revealed NOTCH-gene rearrangements in 50 (54%) GT, 2 MP (18%), and 2 AL (11%). NOTCH-rearrangements were present in 34 (68%) benign and 16 (32%) malignant GT. Fusion-positive benign GT were overwhelmingly seen in males with a predilection for extremities, while the malignant GT occurred mostly in viscera. Among the fusion-negative GT, 88% were benign, 9% uncertain malignant potential, and 2% malignant. Half of the fusion-negative GTs occurred in the finger/subungual region. In summary, rearrangements of NOTCH genes are seen in over half of GT, with NOTCH2-MIR143 being the most common fusion (73%), while only a small subset of AL and MP share these abnormalities. The common subungual GT subset lack NOTCH-gene fusions suggesting an alternative pathogenesis. BRAF-VE1 was negative in all 37 cases studied, while strong PDGFRB staining was seen in 14 (21%) cases. Additional studies are needed to investigate the genetic alterations in the fusion-negative cases.
Source: The American Journal of Surgical Pathology - Category: Pathology Tags: Original Articles Source Type: research