A bone lesion that belongs to the group of osseous (bone building) tumors. Typically afflicted bones are those of the thigh and the shank, but it can also be found in all other skeletal bones, including the vertebrae. As opposed to the majority of benign tumors, this bone lesion is characterized by severe pain, which typically occurs during night time. The origin of the tumor is a tiny, extremely active nucleus in the bone cortex (outer surface), which forms a bony-like tissue and secrets pain-arousing substances. On x-rays the nucleus manifests itself as a radiolucent zone of about 2mm in diameter surrounded by reactive bone formation, which looks like a calcification and condensation of the bone. Technetium bone scan is highly sensitive in detecting the lesion, and will be helpful in establishing the diagnosis. In cases in which the nucleus does not show up on regular x-rays, a CT might be helpful. Treatment can be conservative by the use of anti-inflammatory medications such as aspirin. The bone lesion is self-limited by nature, and its activity ceases after a few years. Sometimes the pain or the amount of drugs required for its relief are intolerable, in which cases, invasive treatment is recommended. This can be achieved by surgical excision of the active nucleus or by means of radio frequency ablation under imaging. Destroying the nucleus immediately brings to relief of pain, and full cure is achieved.