PML immunofluorescence in AML using polyclonal antisera. Phase contrast is shown in left-hand panels and corresponding PML immunofluorescence on the right. In APL cases with cryptic PML-RARα rearrangements, a microparticulate pattern of PML nuclear staining was observed as shown in (a). In non-APL cases, a wild-type pattern of PML nuclear staining was detected, as shown in AML M2 blasts in (b); similar nuclear staining was observed in t(11; 17)-associated APL (case no. 7; Table 1), shown in (c).