This information is provided by the National Institutes of Health (NIH) Genetic and Rare Diseases Information Center (GARD).
Bizarre Parosteal Osteochondromatous Proliferation (BPOP), also known as Nora’s lesion, is an uncommon, benign bone tumor that grows on the surface of the bone. In some cases, BPOP does not cause symptoms. However, at other times, it can be painful and lead to bone deformity. It is more commonly located on the hands and feet, but can also affect the long bones or bones of the skull and face. A biopsy of the affected bone is important, as BPOP may resemble malignant bone tumors, especially chondrosarcoma or parosteal osteosarcoma. The cause is still unknown though injuries or bone defects may trigger the condition in some cases. Treatment involves surgery to remove the tumor. There is a 20%-50% chance that the condition may reappear after surgery.
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