When considering Raman images (Fig. and) and cluster distribution (Fig. ) of each single leukemia subtypes, we can observe that AML M0, associated with an increase of undifferentiated cells (called blasts), exhibits a high nuclearcytoplasmic ratio (see also Fig. ) and with scarce evidence of other components in the cytoplasm, which appear agranular. AML M1 Raman images are like AML M0 but show a lower nuclear-cytoplasmic ratio (Fig. ) and the presence of MPO signals (around 741, 992, 1028, 1540, and 1578 cm -1 ) 20,46,47 in the cytoplasm of several cells, sometimes also prevailing over nuclear (DNA) signals (e.g., around 788 cm -1 ) 14,20,36 . MPO is a peroxidase enzyme, a metalloprotein, expressed by mature granulocytes to produce hypochlorous acid used to deactivate bacteria and other pathogens . This is consistent with the cytological description of AML M1, characterized by an increase of myeloblast with early signs of differentiation in the samples and by MPO positivity after immunostaining.