Phenotypic characterization of atrial myxoma. (a) Typical morphological features of myxoma by hematoxylin and eosin (HE) staining. Myxoma cells were dispersed within abundant myxoid matrix. Scale bar = 100 μm (I), =20 μm (II). (b) Myxoma cells were CD44 and CD19 double positive as confirmed by immunostaining. (c) Immunohistochemical characterization of myxomas revealed that myxoma cells were CD44 and CD45 double positive. Scale bar = 20 μm (b & c).