**1. Introduction**

Chordomas are uncommon, locally aggressive malignant bone tumors that develop from the primordial notochord remnants, accounting for 1–4% of all primary malignant bone tumors [1]. Despite the fact that they can form anywhere along the axial skeleton, sacrococcygeal and spheno-occipital locations are most prevalent, followed by cervicothoracic and coccyx [2]. There are also reports of axial destinations and soft tissue involvement. The spheno-occipital synchondrosis of the clivus is the most common source of intracranial chordomas. The origin can be found along the upper clivus (basisphenoid) or along the clivus' caudal border (basiocciput). Intracranial chordomas can sometimes develop singly from the petrous apex. Chordomas are classified into three categories based on their histological characteristics: classical (conventional), chondroid, and dedifferentiated. Chondroid chordoma is a relatively rare variant that accounts for nearly 14% of all chordomas and is thought to have a better prognosis than classical chordoma [3].

Dedifferentiated chondrosarcoma is a type of cartilaginous tumor that includes two distinct components, namely low-grade chondrogenic components and highgrade noncartilaginous sarcoma. It constitutes 1–2% of all primary bone tumors. Dedifferentiated chondrosarcoma is a rare, highly malignant variant of chondrosarcoma and has a poor prognosis.

Chondrosarcoma is the collective term for a group of heterogeneous, premalignant tumors of bone characterized by the arrangement of hyaline cartilaginous neoplastic tissue. Most conventional chondrosarcomas are low- to intermediate-grade tumors (grade 1 or grade 2). Dedifferentiated chondrosarcoma develops when low-grade conventional chondrosarcoma changes into a high-grade sarcoma, most often showing features of osteosarcoma, fibrosarcoma, or else undifferentiated pleomorphic sarcoma. Mesenchymal Chondrosarcoma (MCS) could be a profoundly malignant tumor showing a Dimorphic histologic design with an exceedingly undifferentiated round cell component admixed with well-differentiated cartilage. The myxoid variant of chondrosarcoma is usually seen in soft tissues, identified as Chordoid sarcoma or parachordoma [4]. Seldom, it includes bone and when it does, cranial bones are the favored location. The prognosis for the majority of patients with chondrosarcoma is relatively favorable and relates to histologic evaluation and satisfactory surgical margins.

In any case, the complex anatomy of the spine and generally expansive tumor volume makes a clean resection ideally challenging, driving to a higher proportion of local relapse as well as distant metastases. Latest disclosures in molecular biology and epigenetics of chordoma and chondrosarcomas have significantly advanced our understanding of the pathobiology of these tumors and offer insight into potential restorative targets.
