Sarcoma is a cancer that develops from supporting tissues found throughout the body (bones, cartilage, etc.). There are more than a hundred: Ewing’s sarcoma, bone, soft tissue… It is a rare cancer in adults, more common in children.
Sarcoma is a malignant tumor that develops in connective tissue, the tissue that supports and protects other organs in the body. Sarcoma accounts for approximately 1% of all cancers that are diagnosed in adults. On the other hand, the proportion of sarcomas is slightly higher in pediatrics (10-12% of all childhood cancers). Sarcomas are extremely complex and above all extremely heterogeneous. In the recognized classifications of sarcomas, there are more than 150 different subtypes of sarcomas well identified, which are extremely different both from a clinical point of view, from an anatomo-pathological point of view (that is to say the appearance of tumor cells under the microscope) and from a biological and molecular point of view.
What is the definition of a sarcoma?
“Sarcoma is a cancer that grows from the supporting tissue, explains Dr. Sarah Watson, medical researcher in the Department of Medical Oncology and the Genetics and Biology of Pediatric Tumors team at the Curie Institute. The support tissue, there is overall all over the body : in the soft tissues, in the viscera and in hard tissues (bones and cartilages). As a result, sarcomas are ubiquitous tumours, i.e. they can develop anywhere in the body.” “Today, they are distinguished and diagnosed on the basis of their essentially anatomo-pathological characteristics (appearance of the cells). If, for example, tumor cells look a little like fatty tissue, we’ll call it a liposarcoma. If the tumor cells look more like a striated muscle tissue, we’ll call it rhabdomyosarcoma (RMS). They are also increasingly distinguished according to their molecular criteria. That is to say that we are going to look for molecular alterations which are really specific to certain subtypes and which are major for the diagnosis and in the choice of treatments.
What are the symptoms of a sarcoma?
THE symptoms are highly variable depending on the location and type of sarcoma. “For a soft tissue sarcoma, the presence of a ball/of a mass of deep location and evolutionary criterion (which moves and grows) must alert and encourage the patient to consult”, adds our interlocutor. It may also have pain, of the transit disorders (in case of intra-abdominal localization), broken bones (bone sarcoma), bone pain, deterioration of general condition, breathing difficulties…
Can sarcoma be cured? What life expectancy?
On average, any type of sarcoma caught in the early, operable, 5-year survival is about 80%. “On the other hand, when the disease is diagnosed at a metastatic stage, 5-year survival rates drop to 15-20%“concludes our interlocutor.
What is a soft tissue sarcoma?
It is a basic clinical distinction that is made at the start: either it is a hard tissue sarcoma (bone, cartilage), i.e. a soft tissue sarcoma (muscle, fatty tissue, viscera, nerves, vessels, tendons, etc.). There is great heterogeneity, different subtypes, depending on the cells, the appearance of the cells and their anatomo-pathological and molecular characteristics.
“The most frequent locations of soft tissue sarcomas are half in the limb (lower or upper), 45% in the trunk (thorax, abdomen or muscles of the chest wall or abdominal wall) and for 5% from the area head and neck“explains the doctor.
What is Kaposi’s sarcoma?
It’s a extremely rare sarcoma subtype which belongs to the family of soft tissue sarcomas. “He goes grow from lymph vessels or blood vessels, explains the specialist. It is characterized initially by cutaneous manifestations with nodular spots on the skin, which have a slightly purplish, brownish color. It can also have manifestations in the mucous membranes (mouth or digestive mucous membranes) and distant metastases such as lung, liver or bone damage. Kaposi’s sarcoma is in the vast majority of cases, linked to a virus infection (HHV8) which very often affects patients with considerable weakening of their immune system. “That’s why we’ve seen an explosion of Kaposi’s sarcoma cases during the AIDS epidemic : the weakening of the immune defenses of affected patients was accompanied by infections with this type of virus and these manifestations. These tumors are treated by multimodal approaches that will combine surgical techniques (when the disease is very localized), at radiotherapy, or at the chemotherapy.
What is Ewing’s sarcoma?
It’s a bone sarcoma. It is the second most common primary bone tumor in adolescents (13 years old) and young adults after osteosarcoma. In more than 90% of cases, this tumor develops from the bone. The most common locations are lower limbs, the pelvis, sometimes the upper limbs or at the costal level. Very rarely, he may have extra-osseous Ewing’s sacomas, which therefore develop in the soft tissues. “It was one of the first sarcomas for which we identified the major molecular anomaly which is responsible for this pathology. It was identified at the Institut Curie by the team of Dr Olivier Delattre who demonstrated that Ewing’s sarcoma was associated in almost 100% of cases with a chromosomal translocation (an exchange of genetic material between 2 chromosomes, 11 and 22). This chromosomal translocation will lead to the fusion of 2 genes, which are normally distinct, and therefore lead to the expression of an abnormal gene called fusion oncogene which will be responsible for tumor transformation and the development of cancer.We are now trying to develop therapeutic approaches which will be based on the biological knowledge of this tumor.” Despite the fact that nearly 30% of patients have metastases at diagnosis, the majority of patients can be cured by combining multimodal approaches (pre- and postoperative chemotherapy, excision of the primary tumor and radiotherapy).
What are the causes of sarcoma?
In the majority of cases, the causes of sarcomas are not known. They are generally sporadic (not associated with particular predispositions). Recognized environmental risk factors include:
- I’exposure to radiation (eg radiotherapy)
- I’exposure to certain chemicals
- A chronic inflammation of a tissue (and in particular chronic lymphoedema)
“The development of a sarcoma can occur only 10 years or 15 years after the occurrence of these exposure factors”, notes Dr. Watson. “And only 1% of sarcomas are associated with very rare hereditary syndromes like Li-Fraumeni syndrome.”
What tests to diagnose sarcoma?
It is a difficult diagnosis because sarcoma is a disease that is poorly understood and rare. “Patients who have a suspicion of sarcoma must be referred immediately to expert centers, insists the doctor. It is the Netsarc network (Expert center for rare cancers labeled by the National Cancer Institute) which has been set up by Professor Jean-Yves Blay. Within these centers, we will be able to do a whole diagnostic assessment which will combine specific imaging (MRI, scanner, even PET-scan to ensure that there are no distant metastases or to characterize the extension of distant metastases) to a pathological examination (biopsy of the lesion). Then pathologists will analyze the biopsy to determine the subtype of sarcoma and decide on the molecular analyzes that will have to be done to correctly type the disease.
What is the treatment for sarcoma?
The treatments are taken care of in one of the 20 expert centers spread throughout France. “The approach is multimodal: the surgery remains the cornerstone of the treatment of sarcomas at a localized stage, associated with radiotherapy for local control (pre or post-operative) and chemotherapy. And for metastatic pathologies (advanced diseases), we will favor systemic treatments, sometimes driven by the biology of the tumors, such as chemotherapy, and for some years now immunotherapy and targeted therapies.
Thank you to Dr Sarah Watson, medical researcher in the Department of Medical Oncology and the Genetics and Biology of Pediatric Tumors team at Institut Curie.