Histological and immunostaining analysis. (A) Low power (10x) and high power (40x, inset) image of an H&E stained representative case of MMTV-RARαG303E Burkitt's lymphoma. (B) The tumor cells stain for PAX-5 (blue). (C) BCL6 staining is negative. (D) Low power (10x) and high power (40x, inset) image of an H&E stained biphenotypic B-myelomonocytic tumor. (E, F) Low power (E, 10x) and high power (F, 40x) image of Pax-5 (blue) and Mac-2 (red) immunostaining showing separate cell populations (same tumor as in D).