Chondroblastoma of the Lower Thoracic Spine. A Case Report and Review of the Literature

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Figure 2. Histological examination revealed that the tumor contains large mononuclear cells mixed with osteoclast-like giant cells growing in a chondroid matrix (hematoxylin and eosin stain, original magnification × 100)

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Figure 3. Anteroposterior (A) and Lateral (B) thoracic radiographs obtained 3 year after operation showing fusion of the arthrodesis

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Follow-up MRI examination in December 2012 revealed that the tumor had locally relapsed without involvement of the spinal canal with high signal areas of the left half of T12 and enhancement after gadolinium injection (Figure 4). The patient was last examined in March 2011. He was clinically well.

Figure 4. MRI of the thoracic spine: sagittal view (T2-weighted image) illustrating local relapse of the tumor

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3. Discussion

Chondroblastoma is a well-known tumor first described by Ewing as a calcifying giant cell tumor in 1928 ^[1] and shown by Codman to be of cartilaginous origin ^[2]. It accounts for about 1% of primary bone tumors ^{[3, 4]} and is considered to be benign with good prognosis in the majority of cases. It most frequently involves the bones around the knee, proximal humerus, and proximal femur ^[5]. Although chondroblastomas occur most often in the epiphysis of the major tubular bones, this tumor can appear in any secondary ossification center, such as greater trochanter. The vertebra also has a secondary ossification center, but it is an exceedingly rare location. To the best of our knowledge, 28 cases of chondroblastoma occurring in the vertebra were reported in the literature, including 19 case reports [6-24]^[6] and one series of 9 cases ^[18]. These cases are summarized in Table 1.

Most of these cases occurred in the lumbar vertebra. This localization represents 1.4% of all chondroblastomas in the file of the Mayo clinic ^[18]. The age range of the patients with vertebral chondroblastoma is from 9 to 62 years with a mean age of 29 years, which suggests that this vertebral localization is clinically apparent a decade later than its appendicular counterpart. The patients in most case reports were predominantly male with a sex ratio of 2.5. Clinical findings of spinal chondroblastoma are usually non specific, including diffuse back pain, neck stiffness or thigtness ^[11], dyspnea due to tracheal compression by the tumor ^[10]. Depending on the extent of spinal cord compression, a wide variety of neurological symptoms and signs may be noted later including pain radiating into fingers, sciatica, muscle weakness and tetraparesis ^{[12, 14, 15]}. The radiological features of vertebral chondroblastoma are not specific. The lesion in imaging appears aggressive and expansive, with almost all cases showing destructive bony lesion with a large soft tissue mass and significant spinal cord compression ^[19]. There are only two reports describing the radiological features of vertebral chondroblastoma ^{[18, 19]}. In a study of 9 patients with spinal chondroblastoma, Ilaslan and al ^[18] noted 7 with tumors on axial imaging showing spinal canal invasion and spinal cord compression. The clue to the cartilaginous nature of the lesion lies in the detection of calcification. Ilaslan et al ^[18] identified calcifications to varying degrees in 7 patients. The body and posterior elements are usually involved.

Table 1. Summary of previous published case reports of vertebral chondroblastoma

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