Notochordal Tumors

Notochordal tumors comprise a spectrum of tumors arising in the axial skeleton having notochordal differentiation characterized by the co-expression of cytokeratin and brachyury. Brachyury is the diagnostic hallmark and is the single most important immunohistochemical marker to differentiate notochordal tumors from chondrosarcoma, myoepithelial tumors, metastasis, and meningioma. The recent WHO classification divides notochordal tumors into benign notochordal cell tumors (BNCTs) and chordomas, which are further divided into three subtypes: (1) conventional chordoma, (2) poorly differentiated chordoma, and (3) dedifferentiated chordoma. BNCT and chordomas have defined histological and radiological criteria and differ significantly in terms of course of disease and management. BNCTs are benign tumors with limited intra-osseous growth, whereas chordomas are slow-growing malignant lesion with progressive destructive growth and capacity for metastasis. Patients with BNCT are generally followed up with serial imaging surveillance. On the other hand, chordomas are treated with surgical excision with negative surgical margin being the most important predictor for survival and recurrence. A distinction between BNCT and chordoma is very important, and it is imperative to detect any early transition of BNCT to chordoma. There is growing evidence that BNCT has a potential for malignant transformation into chordoma, and therefore there is consensus that once identified, these lesions should be carefully followed up over a long period of time to detect any early transformation into chordomas.