Chondroblastoma of bone: case presentation, immunohistochemistry findings and literature review

Chondroblastoma is a rare benign cartilage-producing tu­mor, with an incidence of approximatively 1% of all pri­ma­ry bone tumors. It arises mostly in the second decade of life, affecting mainly the ends of the long tubular bones. We present two cases of chondroblastoma diagnosed and trea­ted in the “Foişor” Orthopedics, Traumatology and Oes­teo­articular TB Clinical Hospital, Bucharest, Romania. The purpose of this study is to contrast two different forms of presentation of the same histologic entity: one case of a 19-year-old male patient with a chondroblastoma lo­ca­ted in the proximal humerus, and the case of a 37-year-old male patient with a chondroblastoma of the cal­ca­neus. The mor­phological fea­tures, radiologic aspects and im­mu­no­his­tochemical stu­dies have been assessed. None of the cases presented with spe­ci­fic radiologic signs for chondroblastoma, both lesions being osteolytic and well-delineated, in favor of a benign en­ti­ty. The classic mor­pho­lo­gical aspects of chondroblastoma re­pre­sen­ted by tumor cells with round poly­gonal shape and nuclei with longitudinal grooves were as­so­cia­ted with variable amounts of chondroid matrix, pe­ri­cellular calcification and few randomly distributed osteo­clast-like giant cells. The im­mu­no­his­to­chemical studies showed the osteoblastic and chon­dro­blastic phenotype of the neoplastic cells, sustained by positivity for CD56 and S100. DOG1, cytokeratin 8/18 and smooth muscle actin (SMA) were also found focally po­si­tive. All cases were treated by curettage with bone graf­ting, without recurrence in the short-term follow-up. Given the nonspecific radiologic findings and the histologic he­te­ro­ge­nei­ty, chondroblastoma is sometimes misinterpreted as a ma­lig­nant tumor, while this neoplastic lesion has a benign be­havior and benefits from conservative surgical treatment only.