BCAS1 and myeloid sarcoma: We evaluated the morphological characteristics of BCAS1-positive cells in MS lesions by distinguishing four lesions subtypes: lesions in which the majority of BCAS1-positive cells showed an activated morphology (Fig. 4a); lesions with BCAS1-positive cells in which the majority of cells showed a quiescent morphology (Fig. 4c); lesions in which both of the cell morphologies were present (activated and quiescent, Fig. 4b), and lesions in which no BCAS1-positive cells were found (Fig. 4d).