Extraskeletal myxoid chondrosarcoma (EMC) is a scarce soft, fleshy muscle or tissue tumor of complex molecular and ultra-architectural characteristics. This kind of sarcoma prognosis is not easy, like other soft tissue sarcomas diagnosed by clinical and radiological findings. This sarcoma has a unique gene fusion (EWSR1-NR4A3) that helps build a differential diagnosis. The reported cases showed that most EMCs appeared in the thigh position, affecting the deep tissues of limb girdles and proximal extremities. Whereas less common occurrences include the head, trunk, neck, pelvis, abdomen, paraspinal soft tissue, and foot, while it rarely occurs in the retroperitoneum, skull, pleura, and bone.
Stout et al. first described the term extraskeletal myxoid chondrosarcoma in 1953, when they presented various chondrosarcoma species. In contrast, Enzinger et al. was the first to propose the EMC concept in 1972. It is classified as a theoretical differentiation tumor and described as a discrete clinical, histological, immunohistochemical, genetic, and evolutive entity.
What is Myxoid Chondrosarcoma?
Extraskeletal myxoid chondrosarcoma, also called EMC, is an uncommon, low-grade cancerous type that grows in soft tissues outside the bone and usually has certain changes in the NR4A3 gene that result in special fusion proteins to be made. They are a type of soft tissue tumor. This diagnostic usually occurs in the thigh but may also occur in the knee, buttock, or trunk (chest and abdomen). They may grow large and expand to nearby tissues or other parts of the body, particularly the lungs. It is usually developed in the deep parts of proximal extremities and limb girdles and occurs more frequently in men than women. They may also reappear many years after the treatment. Extraskeletal myxoid chondrosarcomas usually occur in middle-aged or older adults and are rarely seen in minors and youngsters.
Myxoid Chondrosarcoma – Stages
The two stages of chondrosarcoma can be either localized or metastatic.
Chondrosarcoma is localized in nature when it has not grown out of the bone, where cancer developed. The areas where the cancer is likely to develop can be removed during surgery.
Chondrosarcoma is said to be metastatic when cancer is likely to develop in other parts of the body. The sarcoma most often spreads out to the lungs and other bones.
Myxoid Chondrosarcoma – Prognosis
Due to fewer cases being studied, a multivariate study for the classification of independent prognostic factors could not be performed. Although, the univariate analysis identified some possible markers;
- Tumor size was analyzed as an important prognostic factor, as observed in many other neoplasms: all patients in series who died presented with large tumors (greater than or equals to 10 cm at diagnosis) and developed metastatic disease.
- In some of the described cases, it has been shown that high grade or cellularity is correlated with decreased survival rates. However, other reports have dismissed these findings.
- The studies identified high cellularity and mitotic activity (more than two mitotic figures per 10 HPF) as potential predictors of an unfavorable outcome.
Myxoid Chondrosarcoma – Treatment
To treat this tumor of uncertain differentiation, some studies suggest that radiotherapy is extremely effective in reducing EMC, especially when utilized in affiliation with trabectedin; a potent synergistic outcome could be obtained. However, different treatment methods are needed to cure this rare form of sarcoma. A combination of TKIs and checkpoint inhibitors may be explored in some types of chondrosarcoma and probably this subtype.
Myxoid Chondrosarcoma – Life expectancy
Several research pieces on EMC show that it is usually an inactive, slow-growing tumor. In most cases, patients can survive for extended times, even in the presence of metastatic complications. It has been reported that the patients who have a long-term clinical treatment have a survival rate of 5 years in 90%, ten years at 70%, and 15 years at 60%. However, the results showed some patients could have an advancing clinical course and die shortly after diagnosis. This was illustrated in two of the published cases, where they emphasized the importance of classifying adverse prognostic factors in EMC to handle and treat them better.
Also, the studies confirmed metastasis in nearly 50% of cases, with the most frequent occurrence in the lungs. This is the most common metastasis position in all sarcomas. However, the reported cases had fewer chances of spontaneous regression of pulmonary metastases without any treatment.