Paravertebral extraskeletal myxoid chondrosarcoma: a case report and review of the literature

The extraskeletal myxoid chondrosarcoma (CME) is a rare malignant soft tissue tumour described as a distinct clinical, histological, immunohistochemical, genetical and evolutive entity. It represents only 2.5% of soft tissue sarcomas. Its individualization is important because it has a long and indolent clinical course, and tumour-related death often occurs after a long survival period. The diagnostic key is morphological supported by immunohistochemistry and genetics t (9; 22) that allow differentiating it from other tumours with myxoid stroma and from chordoma. This report describes a patient with paravertebral extraskeletal myxoid chondrosrcoma with a high locoregional extension.


Introduction
Extraskeletal chondrosarcomas were first described by Stout and Verner in 1953 [1]; however, it was not until 1972 that extraskeletal myxoid chondrosarcoma (EMC) was histopathologically defined as its own entity [2]. EMC is provisionally classified as a tumor of uncertain differentiation in the revised version of the World Health Organization classification of tumors of soft tissue and bone in 2002 [3]. EMC is a relatively rare but well-characterized tumor [4]. We report a case of paraspinal location with a high locoregional extension.

Discussion
The CME is a rare entity, distinct clinically, histologically, immunohistochemistry, cytogenetics and scalable. It represents 2.5% of soft tissue sarcomas [5]. Approximately 80% of these tumors occur in the extremities, with 20% located in the trunk. The lower extremity is the most common location of EMC [4]. The male to female ratio of EMC is 2:1, with a peak occurrence in the fifth and sixth decades [4]. EMC is a relatively rare neoplasm with no specific findings in the clinic. Patients commonly present with non-specific symptoms, including tenderness and the detection of a palpable Certain studies have shown that they may also be positive for Leu-7 Page number not for citation purposes 3 and epithelial membrane antigen. Uniformly, they are negative for keratin, SMA and desmin [14][15][16] Genetically, CME is associated in about 80% to recurrent specific chromosome translocation t (9; 22) (q22; q12), leading to a genetic rearrangement between the EWS gene, located on chromosome 22 and the gene TEC, located on chromosome 9 [11]. The rearrangement can be searched by RT-PCR on fixed tissue. Other translocations are rarely observed [5]: t (9; 15) (q22; q12), t (9; 17) (q22; q11.2), t (9; 17; 15) (q22; q11 ; q22), t (2; 13) (q32; p12) and t (11; 22) (q11; p11) [17]. Recognition of the histologic features of conventional EMCS that are present, at least in part, is most important for a differential diagnosis. Ancillary approaches such as immunohistochemistry and electron microscopy are also valuable [5]. Treatment is firstly surgery of the initial tumor and / or metastasis, radiotherapy and chemotherapy as first-line have not been proven [18]. This tumor does not respond to chemotherapy and the results concerning radiotherapy are discordant [19].
The development of CMES is difficult to predict. Nearly half of patients have one or more local recurrences within an average of 44 months [20]. Survival after the onset of metastases is very varied in duration, on average 66 months. Although the five-year survival rate is quite high, metastases are common (46-90% of cases) and long-term prognosis is adverse (30-70% survival at ten years) [20,21]. Metastases occur in order of decreasing frequency, in lungs, soft tissue, lymph nodes, bone, and brain. The main poor prognostic factors are the occurrence in man, the late age of onset, tumor size greater than 10 cm, proximal seat, the incompleteness of the initial surgical resection, the absence of surgical resection and discovery of metastases at diagnosis [11,20]. The histoprognostic criteria such as necrosis, mitotic activity, the degree of differentiation does not appear to influence the outcome [22]. In fact, these criteria are discordant in the literature and are controversial subjects.

Conclusion
The CME is a rare entity, distinct clinically, histologically, immunohistochemistry, cytogenetics and scalable. The diagnostic key is morphological, aided by immunohistochemistry and genetic study.

Competing interests
The authors declare no competing interests.

Authors' contributions
All authors read and approved the final version of the manuscript. and heterogeneous high signal in T2WI