Morphology and immunohistochemistry of BL primary tumors and cell lines. (A) May-Grunwald Giemsa staining of cytologic smears showing the characteristic intracytoplasmic vacuoles. (B) Immunohistochemistry of BL primary tumors showing cytoplasmic localization of the pRb2/p130 protein suggestive of mutations within the nuclear localization signal. Immunohistochemistry of BL cells transfected with either the empty vector (C) or RBL2/p130 (D). Cytoplasmic localization of the pRb2/p130 protein is observed in empty vector–transfected cells whereas RBL2/p130-transfected BL cells show normal nuclear expression of pRb2/p130. Images were viewed by means of a Zeiss Aski Axioskop 40 microscope equipped with a Zeiss Axiocam H Rc (panels A, C, and D, 40×/0.65 NA; panel B, 63×/0.80 NA) (Zeiss, Vertrieb, Germany) and processed using Axiovision (Zeiss) software. Original magnification: panels A, C, and D, × 750; panel B, × 970.