The authors report on a 34-year-old man who presented with acute enlargement of an extraspinal mass secondary to a hemorrhage following minor trauma. The mass had been present from birth, had slowly enlarged over time, and previous imaging had suggested an extraspinal fibrolipoma measuring 10 x 6 x 4 cm. Following minor trauma (scratching the skin overlying the tumor), the mass rapidly enlarged to approximately double in size over a period of 4 hours. A CT scan and MR imaging confirmed an extraspinal tumor that was 15 x 11 x 11 cm, with an associated acute hematoma of similar dimensions. The patient was taken to the operating room for hematoma evacuation and tumor resection. Histopathological investigation identified a benign, diffuse neurofibroma with associated dysplastic blood vessels exhibiting irregular areas of tunica media and sinusoidal-like vascular channels. To the authors' knowledge, a solitary giant neurofibroma in a patient without neurofibromatosis presenting with acute enlargement secondary to hemorrhage following minor trauma has not been previously described. The authors suggest that the source of the acute hemorrhage may be related to the neurofibroma-associated vascular dysplasia and the resultant increased vascular fragility.