SS are rare and aggressive soft tissue tumors that usually affects adolescents and young adults. It rarely presents in the spine and primary bone origin is even rarer with sparse cases reported in the literature. Therefore, there are no specific studies on primary bone origin SS and therapeutic approach is extrapolated from studies involving other types of SS and other aggressive types of sarcoma.
It is widely accepted that the most effective treatment is a complete margin free, block excision. Adjuvant radiotherapy seems to decrease local recurrence and seems beneficial both in patients with complete resections and marginal resections [2, 8, 13].
In our case, due to the fast progressive clinical deterioration, a decompressive intervention was performed by C3 and C4 corpectomy, piecemeal resection of identifiable intracanalar tumor mass and anterior cervical fusion from C2 to C5.
Chemotherapy schemes based on anthracycline, alone or combined with ifosfamide can be used in advanced disease [2, 8]. Despite most of the studies not showing statistical differences in the global survival rate in patients with aggressive sarcomas treated with adjuvant chemotherapy [15–18], Ferrari A. et al , in a retrospective study that included 271 SS patients, showed that patients treated with adjuvant chemotherapy had a longer metastasis free survival rate compared to patients submitted to surgical treatment only, suggesting it may have a role in the prevention of metastatic disease.
Chemotherapy and radiotherapy may also have a role in tumor size reduction in the preoperative period for unresectable SS. Radiotherapy has a well-established role in improving local control, especially after less-than-compartmental resection. 
SS survival rates are best in young patients and those in whom a complete margin free resection is achievable. Worse prognosis is associated with no margin free resection, advanced age (> 25 years), tumor dimension greater than 5cm, tumor necrosis, vascular invasion, lower cellular differentiation, and high mitotic index [8, 11, 13].
Histologically, SS is composed mainly by two different cell types, epithelial and spindle cells. Depending on the proportion of each of the components and the degree of differentiation of them, SS can be categorized into biphasic, which comprise the two cell types in varying proportions, or monophasic, most of which consist of spindle cells. A third undifferentiated round cell type has been described (can comprise up to 20% of the cases) which represents a form of tumor progression that can occur in both single-phase and biphasic tumors and has a more aggressive behavior [1, 2, 8].
SS immunophenotypic examination is usually positive pro EMA and several cytokeratins, in particular CK7 and CK19 whose expression is not observed in other sarcomas. The expression of these three markers is intense and diffuse in the epithelial and focal component and dispersed in the spindle-cell component and in the poorly differentiated type. SS also shows positivity for CD99, bcl-2 and TLE1. In about 30% of cases, focal positivity is observed for the S100 protein and very rarely in the spindle component, CD34 expression is observed [2, 8]
Genetically, SS is characterized by the translocation t(X,18) that merges the SS18 gene (also known as SYT) with the SSX1 (the most common variant), SSX2 or SSX4 genes, on the X chromosome. The sensitivity and specificity for the diagnosis of SS is well established [8, 13]. In up to 5% of the cases, SS have the typical clinical and morphological characteristics but does not carry any of the SS18-SSX fusion gene .
In our case, the histological examination showed histological characteristics compatible with the diagnosis of biphasic synovial sarcoma, as well as an immunophenotype described in the literature as more frequent in this type of tumor, namely positivity for EMA, CK19 and CD99. The cytogenetic testing was negative for the translocation t(X,18).
Patient age (55 years), delay in the diagnosis, histological analysis with tumor necrosis, high mitotic index, marginal resection and distant disease (involvement of submandibular ganglia) culminated in a very poor prognosis case. Despite evidence showing potential beneficial effects of both chemo and radiotherapy in incomplete resections and with distant disease, our multidisciplinary oncology team decided not to immediately initiate adjuvant therapy due to patient cardiorespiratory debilitation.
Additionally, tumor location on high cervical spine, with spinal cord compression and consequent ventilatory mechanics impairment that led to the need of an emergent decompression surgery, greatly contributed to aggravate the already poor prognosis.
Yang M et al , reported the largest series of spine SS to our knowledge, with 16 cases in a period of 10 years practice. Only in four cases they achieved a block resection of the tumour, demonstrating that this can be very challenging in the spine due to the complex vertebral anatomy and surrounding structures.
Recently, new therapeutic strategies are emerging [8, 19]. Pazopanib (a multitarget tyrosine kinase inhibitor) has been approved for the treatment of adult patients with advanced soft tissue sarcomas including SS. Other potential targets are the SS18-SSX fusion and New York esophageal squamous cell carcinoma 1 (NY-ESO-1), that is expressed by several tumors and is present in nearly 60% of SS . New studies on these and new potential targets are ongoing.
A high suspicion level is essential for the diagnosis of these lesions to identify them early in order to allow multidisciplinary treatment planning and improve prognosis.