Introduction 1 2 3 6 Materials and methods 1 Table 1 Antibodies used in the study Antibodies Source Clonality Dilution Epithelial membrane antigen DAKO Cytomation, Glostrup, Denmark M 1:100 Cytokeratin (AE1/AE3) DAKO Cytomation, Glostrup, Denmark M 1:100 Cytokeratin (CAM5.2) Becton Dickinson, San Jose, CA, USA M 1:1 Cytokeratin 18 DAKO Cytomation, Glostrup, Denmark M 1:20 Vimentin DAKO Cytomation, Glostrup, Denmark M 1:100 S-100 protein Nichirei, Tokyo, Japan P 1:200 M, monoclonal; P, polyclonal Results 2 1 2 7 8 3 4 Table 2 Summary of benign notochordal cell tumors found clinically Patient Age (years) Gender Location Symptoms Treatment Original diagnosis Follow-up information 1 30 Male L4 Low back pain Vertebrectomy following biopsy and curettage Chordoma Alive with no evidence of disease, 60 months 2 53 Female C6 Numbness and pain of the fingers bilaterally, probably due to OPLL at C6, 7 Vertebrectomy following biopsy Chordoma Alive with no evidence of disease, 57 months 3 55 Female C5 Neck pain, shoulder stiffness Biopsy Chordoma Alive with no progressive disease, 13 months 4 50 Male C3 Car accident injury (incidentally found on MRI) Curettage Osteonecrosis Alive with no evidence of disease, 84 months 5 52 Male C5 Mild upper back pain OPLL, focal Needle biopsy Osteonecrosis Alive with no progressive disease, 44 months 6 22 Female S4, Cox (microscopic) Buttock pain Wide resection following curettage Chordoma Alive with no evidence of disease, 17 months 7 43 Female L5, S2 Car accident injury (incidentally found on MRI) Vertebrectomy following biopsy at L5 Chordoma Died of postoperative complications L, lumbar vertebra; C, cervical vertebra; S, sacrum; Cox, coccyx; OPLL, ossification of posterior longitudinal ligament Fig. 1 a b c d e  Fig. 2 a b c d  Fig. 3 a b  Fig. 4 a b  Imaging findings n n n n 1 2 3 1 2 1 3 1 Histological findings 5 5 5 5 5 4 5 Fig. 5 a b c d e  Discussion 1 2 9 11 1 2 9 10 1 2 9 11 3 6 12 4 5 4 5 3 1 2 9 10 11 Table 3 Imaging and microscopic features of benign notochordal cell tumors Evaluation method  Features n n n n n n n n n n n n n n n Solid sheets of adipocyte-like vacuolated cells combined with less vacuolated eosinophilic cells of various degrees Round or polygonal pyknotic nuclei occasionally with polymorphism No lobular configuration No extracellular myxoid matrix Some cystic spaces containing eosinophilic colloid-like material No mitotic figures Poor vascular network Entrapped islands of hematopoietic bone marrow Sclerotic bone trabeculae affected Positive immunostaining for vimentin, cytokeratin (AE1/AE3, CK18), EMA, and S-100 protein CT, computed tomography; MR, magnetic resonance; WI, weighted image; Gd; gadolinium; CK, cytokeratin; EMa, epithelial membrane antigen. 13 3 3 Diagnosis of the cases presented was based upon biopsy or preoperative imaging; the diagnosis was chordoma in 5 cases and osteonecrosis in 2. Hence, 5 patients underwent vertebrectomy, wide resection, or curettage. All patients but 1 are well without recurrent or metastatic disease. Two patients who underwent only biopsy had no progressive disease, as judged by radiography, CT, or MR images, for 13 months and 44 months respectively. As described by Mirra and Brien, the follow-up information was consistent with the benign nature of the tumors. 11 9 10 2 9 3 14 2 11 15 16 3 5 17 6