SS18::POU5F1-fused sarcoma is an exceedingly rare malignant tumor, with only isolated case reports documented to date. We present the first reported case of SS18::POU5F1 fusion sarcoma occurring in the left submandibular gland of a middle-aged male patient. The tumor exhibited multiphasic differentiation, including epithelioid cells and undifferentiated round cell components, with focal evidence of neural differentiation and Flexner–Wintersteiner rosettes. It was characterized by the presence of a SS18::POU5F1 gene fusion. We provide a detailed description of the clinical features, histomorphology, immunophenotype, molecular characteristics, treatment, and prognosis of this case, discuss its differential diagnosis and potential pathogenesis, and include a comprehensive review of the relevant literature.
Niu et al. (Thu,) studied this question.