[en] An extremely rare example of an elongated (3 cm) osteoid osteoma is presented. The tumor demonstrated three focal enlargements connected by narrow areas, suggesting a ''string of beads'' in appearance. The elongated shape suggested the possibility that lesional tissue was stretched in a longitudinal fashion as a result of the rapid skeletal growth. The tumor closest to the growth plate was densely ossified, while the furthest lesion was almost completely lytic, suggesting that the tumor enlarged in a centripetal direction. This case is believed to illustrate a continuum from solitary to multicentric osteoid osteoma. The tumor was treated successfully with three separate percutaneous radiofrequency ablations during a single session. (orig.)