This is a specimen of stalk resection of pedunculated bony swelling. Diagnosis is

Osteochondroma, also known as an exostosis, is the most common benign bone tumor; about 85% are solitary.It is a benign cailage-capped tumor that is attached to the underlying skeleton by a bony stalk. The cap is composed of benign hyaline cailage varying in thickness and is covered peripherally by perichondrium. The coex of the stalk merges with the coex of the host boneRef: Robbins Pathology; 9th edition; Page no: 1200