Pediatric Angiosarcoma with Novel Phenotypic and Genotypic Profile in Chinese Children

<b>Introduction:</b> Angiosarcoma is an exceedingly rare entity in pediatric population. Herein, we report two pediatric angiosarcoma with novel phenotypic and genotypic profile. <b>Methods:</b> The two patients' information was summarized by clinical data, histopathology, immunohistochemistry, genetic, treatment, and prognosis. <b>Results:</b> Two Chinese children presented with abdominal mass or consumptive hypothyroidism at 2 and 6 years. A patient presented with a unique histopathology of epithelioid AS with smooth muscle hyperplasia, and carried a novel somatic mutation in <i>FAT1</i> (c.3929C <i>></i> T/p. Ser1310Leu) along with germ-line variants in <i>CDK8</i> (c.895A <i>></i> C/p. Lys299Gln), <i>FANCI</i> (c.3906-07inv/p. Glu1303Lys), and <i>MST1R</i> (c.3581-83delinsACG/p. Arg1194-Ser1195delinsHisGly). The other patient presented with a novel -clinical phenotype of consumptive hypothyroidism. They received postoperative treatment and were monitored for 20 and 26 months, showing good recovery. <b>Conclusion:</b> The phenotypic and genotypic spectrum of AS in pediatric population was expanded by these two patients, which requires the accumulating more cases to gain a deeper understanding.