Benign active lesions may have been present in the bone for substantial periods of time and exist in a type of symbiosis with the skeleton.
- The best example is fibrous dysplasia, which may be present for a lifetime and cause minimal symptoms. However, the lesion is not always contained by reactive surrounding sclerosis, and it is possible for the bone to fracture in response to minimal trauma.
- This description applies to active unicameral bone cysts and non-ossifying fibromas that may cause pain and present a risk for fracture in children.
- Another example is an osteoid osteoma. Such lesions are usually active and symptomatic, causing pain but limited destruction of the host bone. After several years osteoid osteomas may cease to be symptomatic and become latent.