The clinical photograph, images, and histology slide are consistent with a diagnosis of chondroblastoma, a benign aggressive cartilage tumor which most commonly occurs in the second decade of life. The radiographs and MRI show a lytic epiphyseal lesion with a surrounding sclerotic border. The characteristic histology slide shows the "cobble stoning" pattern of monotonous cells (looking like a cobble stone road) with stromal based "chicken-wire" calcification and a few scattered giant cells. While all the other options may occur in the epiphysis, the size, bone edema, MRI intensity, and the histology slide are characteristic of chondroblastoma.
Video Illustration demonstrates a pathologist reviewing the histopathology of chondroblastoma.
Giant cell tumor - while also can be epiphyseal in location, GCT typically occurs in older patients and shows a different histology profile with giant cells whose nuclei appear identical to the neoplastic monocytic cells
Clear cell chondrosarcoma - while also epiphyseal in location, again the histology in clear cell chondrosarcoma is diagnostic and different from chondroblastoma with more cellular atypia and chondroid formation
Brodie's abscess - the histology would show neutrophils on histology and may or may not culture positive for microorganisms
Osteochondral defect - is an area of damaged cartilage in the joint and would appear different on radiographs, MRI, and histology
Simon MA, Springfield D. Surgery for Bone and Soft-Tissue Tumors. Philadelphia, PA: Lippincott-Raven; 1998:190-191.
Springfield DS, Bolander ME, Friedlaender GE, Lane N. Molecular and cellular biology of inflammation and neoplasia. In: Simon SR, ed. Orthopaedic Basic Science. Rosemont, IL: American Academy of Orthopaedic Surgeons; 1994:219-276.