(A,B) H&E appearance. (C,D) α Smooth Muscle Actin (αSMA) immunohistochemical staining. (E,F) RGS5 immunohistochemical staining. (G,H) CD146 immunohistochemical staining. (I,J) PDGFRβ immunohistochemical staining. Black arrowheads indicate atypical enlarged stromal cells with positive staining. Black scale bar: 100 µm.