[Chondroblastoma occurring in atypical sites].
OBJECTIVE
To study the clinical, pathologic and radiologic features of chondroblastoma occurring in sites other than epiphysis and apophysis of long bones, and to investigate possible reasons for misdiagnosis.


METHODS
The clinical, pathologic and radiologic data of 18 chondroblastoma cases occurring in atypical sites were collected from 5 major hospitals in Shanghai during the past 12 years. S-100 immunostaining was performed to confirm the cartilaginous differentiation of the tumor cells.


RESULTS
Chondroblastoma occurred in small bones of feet in 10 of the 18 cases (55.6%) studied, being commonest in the talus and calcaneus bones. Mean age of the patients was 27.8 years, with 55.6% over 25 years of age. Radiologic examination revealed expansive, multilocular and well-demarcated radiolucent lesions in most cases. There was local cortical destruction in 5 cases (28%) and soft tissue infiltration in 1 case. In 10 cases (55.6%), the tumor was associated with aneurismal bone cyst or simple bone cyst formation. None of the cases studied was accurately diagnosed clinically before the operation. In 2 cases, the pathology was also misdiagnosed, often being diagnosed as aneurismal bone cyst or giant cell tumor.


CONCLUSIONS
Chondroblastoma occurring in atypical sites are often associated with atypical age, radiologic features and pathologic findings at presentation. Thorough understanding of the potential pitfalls is essential in order to avoid misdiagnosis.
Jiang
Zhi-Ming
ZM
Department of Pathology, Shanghai Sixth People's Hospital Attached to Jiao Tong University, Shanghai 200233, China.
Zhang
Hui-Zhen
HZ
Tan
Yun-Shan
YS
Tang
Ru-Yong
RY
Liu
Hui-Min
HM
Lu
Shao-Hua
SH
Shu
Mo-Juan
MJ
Zeng
Bing-Fang
BF
Yang
Shi-Xun
SX
Chen
Jie-Qing
JQ
Huang
Jin
J
D000293:Adolescent; D000328:Adult; D017824:Bone Cysts, Aneurysmal / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000473:pathology; D001847:Bone Diseases / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology; D001859:Bone Neoplasms / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology; D002111:Calcaneus; D002648:Child; D002804:Chondroblastoma / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology; D003951:Diagnostic Errors; D005260:Female; D018212:Giant Cell Tumor of Bone / Q000000981:diagnostic imaging / Q000473:pathology; D006801:Humans; D008297:Male; D011859:Radiography; D013628:Talus