Malignant degeneration frequently arises from preexisting plexiform neurofibroma in patients with neurofibromatosis type 1 (NF1). Image guided biopsy for diagnostic purposes, such as with CT guidance, can be technically challenging in these patients, as CT cannot distinguish malignant from benign areas within the same tumor. Navigation with multi-modality (PET, CT, and ultrasound) image fusion facilitated the successful biopsy and diagnosis of angiosarcoma arising from a pelvic neurofibroma in a patient with NF1. Successful targeting assisted treatment selection in this case. This novel navigation technique may facilitate the otherwise difficult diagnosis of malignancy in patients with NF1. Pediatr Blood Cancer 2013;60:E166–E169. © 2013 Wiley Periodicals, Inc.