"Aggressive" chondroblastoma. Light and ultramicroscopic findings after en bloc resection

A chondroblastoma of the proximal humerus in a 15-year-old boy was removed en bloc due to its very large size and locally destructive, aggressive character. This case is reported because of the rarity of chondroblastomas excised en bloc; specimens were examined in detail by correlated roentgenographic, gross inspection, histologic and electron-microscopic methods.