D2I2.
benign-tumour

Osteochondroma

Osteochondroma is the most common tumor of bone. The take the form of -capped bony projections or outgrowth on the surface of bones (exostoses). It is characterized as a type of overgrowth that can occur in any bone where cartilage forms bone. Tumors most commonly affect long bones around the knee and in the forearm. Additionally, flat bones such as the and scapula may be affected.

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Plain-language summary adapted from Wikipedia. Not medical advice.