A 4-year-old boy from Brazil is brought to the physician because of a 1-week history of painless swelling of his jaw and pressure around his eyes. He is at the 80 th percentile for height and…

A 4-year-old boy from Brazil is brought to the physician because of a 1-week history of painless swelling of his jaw and pressure around his eyes. He is at the 80 th percentile for height and weight. Physical examination shows a single 12 ? 10-cm lesion in the right side of the jaw with diffuse limits and irregular edges. Photomicrographs of an incisional biopsy specimen of the lesion are shown. Based on these findings, which of the following processes is most likely occurring in the region indicated by the arrows?