The sarcomas represent 1% of all cancers in adults, 8% in adolescents and young people, and 10% in children. Even though it is a rare cancer, it contributes to a significant loss of years of life in comparison with other types of cancer, due the fact that it affects children and young people. The diagnosis and treatment are difficult, considering the diversity and rarity of this disease. In addition, on average, more than 50% of patients with high-grade sarcoma present tumor relapse and distant recurrence is considered the main cause of death. The presence of Circulating Tumor Cells (CTCs) in the blood of patients with sarcoma may be an early marker of tumor invasion, because it is known that the CTCs circulate in the blood for months or years before the development of metastases. The CTCs can be used to monitor the response of the tumor to treatment, in order to match time, dose, and type of therapy.

Objectives: collect blood from patients with different types of sarcoma (leiomyosarcoma, synovial sarcoma, pleomorphic sarcoma and liposarcoma) in order to isolate and quantify CTCs. The investigators also have an intention to identify genes of resistance to treatment in these cells.

Methodology: This is a prospective study, to be made by whole blood collection from 40 patients with different types of sarcomas (leiomyosarcoma, pleomorphic sarcoma, synovial sarcoma and liposarcoma). The collections will be made in three different moments: before the beginning of the treatment, during and at the end of this (8 mL). Blood samples will be processed and filtered on ISET system for the isolation and quantification of CTCs. Later, it will be performed immunocytochemistry (ICQ) single and/or double staining for protein assessment. The following proteins will be assessed: CD45, MRP1, MRP2 and MRP7.

Expected Results: The investigators hope that this study can show if the CTCs can be used as "liquid biopsy" in patients with leiomyosarcoma, synovium and pleomorphic sarcoma and liposarcoma.

Inclusion Criteria:

• 18 years or more;
• types of sarcomas: leiomyosarcoma, pleomorphic sarcoma, synovial sarcoma and liposarcoma.
• extension of the disease determined by physical examination and imaging;
• measurable disease by RECIST criteria (Response Evaluation Criteria in Solid Tumors);

Exclusion Criteria:

• patients who have undergone previous therapy in the last three weeks;
• patients with a history of other cancer in the past two years.

patients with 4 types of metastatic sarcomas: leiomyosarcoma, pleomorphic sarcoma, synovial sarcoma and liposarcoma.