PMC10175838_01
Axial MRI Imaging. (A) Well-circumscribed fusiformmass is noted in the left lower eyelid appearing hypointense on T1 weighted image with green arrowhead. (B) T2-weighted showing hyperintense with green arrowhead.
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MRI scan revealed a subcutaneous mass (1.2 x 0.5 cm) in the left lower eyelid, which was well demarcated indicating a pre-operative clinical impression of skin benign tumor ( Figures 1A, B ).
Representative H&E and IHC stainings of serial sections. (A) Extra-low power H&E image shows a well-demarcated mass entirely, surrounded by fibrous pseudocapsule. (B) High power view of A gets more detail about the pseudocapsule, simultaneously, demonstrates hyperendothelial vessels and lymphocytes that aggregated around these vessels. (C) The tumor is primarily composed of primitive round cells with scant cytoplasm and numerous mitosis. (D) Focally shows clear cytoplasm and lymphocytes aggregating around the hyperendothelial vessels. (E) Diffuse Desmin staining in the same power view of (A, F) A high power view of E showing cytoplasmic positive of Desmin, while the nonmuscular hyperendothelial vessels are negative for Desmin. (G, H) Focal positive immunohistochemical staining of tumor cells for MYOD1 and Myogenin respectively. (I, J) The immunohistochemical staining for TrkA/B/C expression was performed using pan-Trk (clone EPR17341, Roche/Ventana). There is a strong diffuse immunoreactivity for pan-Trk in cytoplasm of tumor cells. (K, L) Negative IHC reaction for CD34 and S100, respectively.
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After surgical excision of subcutaneous tumor, samples were micro-evaluated in our department, and presented as monomorphous population of primitive cells with abundant mitosis and minimal cytoplasm ( Figures 2A, C ). The mass was surrounded by a continuous fibrous pseudocapsule ( Figures 2A, B ). Hyperendothelial vessels lied in maliglant tumor cells, with small lymphocytes surrounding these vessels ( Figures 2B, D, F, G, H, K, L ). DES, MYOD1 and Myogenin showing patchy staining) ( Figures 2E-H ), which led to reliable diagnosis of ERMS in the case. DNA-based NGS revealed MEF2D-NTRK1 (EX5:EX12) fusion ( Figure 3A ), and NTRK1 amplification, along with multiple genes amplifications (CDK6, PMS2, MET, EGFR, BRAF, MLL3, MYC, FGFR1, WRN, EXT1, NBN, RECQL4) and deletions (FLT4, MAP2K2, DOT1L, STK11, GNA11) ( IHC staining of pan-Trk was performed, as expected, it demonstrated diffusely strong positive in cytoplasm ( Figures 2I, J ). In terms of differential diagnosis in IHC, CD34 and S-100 were negative ( Figures 2K, L ).
NGS testing of the tumor to validate NTRK1 fusion. (A) DNA-based NGS testing of the pan-tumor related 1021-Genes Panel is used to demonstrate the MEF2D-NTRK1 (EX5:EX12) fusion in formalin-fixed paraffin-embedded tissue sample. (B) Schematic representation of the predicted chimeric protein in RNA-based NGS assay with the 555-Genes Panel in formalin-fixed paraffin-embedded tissue sample.
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Next, RNA-based NGS also revealed MEF2D-NTRK1 (EX5:EX12) fusion ( Figure 3B ).