Chondroblastoma is a rare benign cartilage-producing tumor consisting of about 1% of all bone tumors [3]. Chondroblastoma is usually found in the epiphyseal or epimetaphyseal areas of long bones, in males (male:female ratio 2:1), and could be found in any ages, even if it occurs most frequently between 10 and 25 years old. The incidence of vertebral chondroblastoma is 1.4% of all chondroblastomas, and less than five cases of sacral involvement have been reported in literature (only one clearly described) [27]. The radiological findings of vertebral chondroblastomas are nonspecific and biopsy should be performed considering possible more frequent differential diagnosis: aneurysmal bone cyst, giant cell tumor, chondromyxoid fibroma, osteoid osteoma, osteoblastoma, chondrosarcoma, chordoma, and metastasis [3]. Chondroblastomas of the spine behave more aggressively than those of long bones with a higher rate of local recurrence (about one-third of patients) [27–30]. Some authors suggested that this may be related to the frequent extension to adjacent soft tissue and the spinal canal, which precludes complete tumor resection [31, 32]. Three cases of tumor-related death have been reported due to direct invasion to adjacent soft-tissue and neurological structures [27, 30, 33]. Therefore, complete excision and long-term follow-up are generally recommended as the treatment modality for vertebral or sacral chondroblastomas.

Chondromyxoid fibroma (CMF) is a rare benign cartilaginous tumor generally observed between 5 and 30 years of age. It accounts for about 0.5% of all primary bone tumors [3, 34]. CMF of the sacrum is exceedingly rare, with less than ten cases reported in the literature (Table 13.2) [35–43]. Many of them demonstrate expansile or erosive imaging pattern, with cortical destruction, sclerotic and lobulated borders, septation, and intralesional calcifications [34]. Because of these radiographic similarities with more aggressive sacral pathology, differentiating CMF from chondrosarcoma, chordoma, and giant cell tumor on the basis of imaging alone is not possible [40]. CT-guided biopsy with histologic evaluation is mandatory for diagnosis. Although follow-up and detailed documentation are rather lacking in the treatment of sacral CMF, surgery in terms of total en bloc resection or intralesional curettage represents the current accepted management options. Radiation therapy has been used for sacral CMF in only one patient who died of complications before 4 months of follow-up [37]. The risk of local recurrence for CMF ranges between 4 and 80% [41], but higher risk can be expected in younger age group with spine lesions despite extensive curettage [36]. The longest reported follow-up for sacral CMF was a patient treated with curettage and bone grafting, who was found to be recurrencefree at 8-year follow-up [38]. Other authors reported no evidence of recurrence at about 1 year of follow-up after wide resection [40, 42].