Phase II, open-label, non-randomized, international multicenter clinical trial with two strata (SFT and EMC). 8 sites in Spain, 5 sites in Italy and 5 sites in France. Patients will receive oral pazopanib at 800 mg once daily continuously. Patients will continue to receive treatment until there is evidence of progressive disease, unacceptable toxicity, non-compliance, withdrawn consent or investigator decision. The main goal is to determine the objective response rate (ORR) (confirmed complete response [CR] and partial response [PR]) in patients with unresectable, locally advanced or metastatic solitary fibrous tumor and extraskeletal myxoid chondrosarcoma, using Choi and RECIST 1.1 criteria respectively.

To estimate the sample size for stratum 1 (SFT), a Simon's optimal 2-stage phase II design has been used, having considered the published response rate based on Choi criteria in SFT patients which correspond to 40% in monotherapy. For a design with P0=0.40, P1=0.60; α=0.1 and β=0.1. At the first stage, 18 patients should be enrolled into the study, if there are fewer than 8 responses (7 or less) the trial will be terminated and it will be concluded that pazopanib is not sufficiently active. At the second stage, another 28 patients (total 46 patients) would be enrolled into the study. To reject the null hypothesis for the SFT stratum 23 responses or more (Choi criteria), out of the 46 patients, are needed.

To estimate the simple size for stratum 2 (EMC), a Simon's optimal 2-stage phase II design has been used, having considered the very scarce published information on response rate based on RECIST criteria. For a design with P0= 0.05, P1= 0.25, α=0.1 and β=0.1. At the first stage, 9 patients should be enrolled into the study, if there are not responses the trial will be terminated and it will be concluded that pazopanib is not sufficiently active. If there is at least 1 response in this first stage, the trial will be continued and at the second stage, another 15 patients (total 24 patients) would be enrolled into the study. To reject the null hypothesis for the EMC stratum 3 responses or more (RECIST criteria), out of the 24 patients, are needed.

For variables that follow binomial distributions (e.g. response rate) frequency and percentages will be calculated, together with their corresponding exact 95% confidence intervals. For time-to-event variables (e.g. PFS or OS) Kaplan-Meier estimations will be used. To analyze the reduction of risk and the influence of other variables on time-to-event variables Cox Regression will be applied. To correlate pharmacodynamics markers and biomarkers with clinical response standard methods for bivariate and multivariate regression and correlation will be used.

Inclusion Criteria:

• Informed consent prior to performance of study-specific procedures or assessments and must be willing to comply with treatment and follow up.
• Age ≥ 18 years or legal age of consent if greater than 18 years.
• Histologic diagnosis of solitary fibrous tumor (stratum 1) or extraskeletal myxoid chondrosarcoma (stratum 2) (unresectable, locally advanced or metastatic disease) confirmed by central pathology review.
• Patients with metastatic tumor suitable for complete resection can be recruited. In absence of progressive disease these patients should be treated with the study drug for at least 6 months.
• For patients who have received previous anticancer treatments, progressive disease must be demonstrated within 6 months prior to enrollment.
• Eastern Cooperative Oncology Group (ECOG) performance status of 0-2.
• Measurable disease according to Choi (SFT) and RECIST 1.1 (EMC) criteria.
• Patients could have received a maximum of 4 lines of chemotherapy for metastatic disease prior to trial enrollment.
• Patients must be able to swallow and retain the study drug.
• Adequate organ system function as defined in protocol.
• Women of childbearing potential must have a negative serum or urine pregnancy test within 7 days of first dose of study treatment. All patients (both male and female) must agree to use effective contraception methods, as defined in the protocol.
• Left ventricular ejection fraction (LVEF) above the lower limit of normal for the institution, either by echocardiogram or MUGA.
• Patients in France will be eligible for inclusion in this study only if either affiliated to or a beneficiary of a social security category.

Exclusion Criteria:

• Prior malignancy, except patients who have had another malignancy and have been disease-free for 10 years, or those with a history of completely resected non-melanomatous skin carcinoma or successfully treated in situ carcinoma.
• Central nervous system metastases at baseline, with the exception of patients who have previously-treated central nervous system metastases (surgery ± radiotherapy, radiosurgery, or gamma knife) and who meet both of the following criteria: a) are asymptomatic and b) have no requirement for steroids or enzyme-inducing anticonvulsants in prior 6-month time interval.
• Patients who have received previous antiangiogenic agents.
• Significant gastrointestinal abnormalities that may increase the risk for gastrointestinal bleeding.
• Significant gastrointestinal abnormalities that may affect absorption of investigational product.
• Corrected QT interval (QTc) > 480 msecs.
• History of any one or more of the following cardiovascular conditions within the past 6 months:

Cardiac angioplasty or stenting Myocardial infarction Unstable angina Coronary artery bypass graft surgery Symptomatic peripheral vascular disease Class II, III or IV congestive heart failure, as defined by the New York Heart Association (NYHA)

• Poorly controlled hypertension [defined as systolic blood pressure (SBP) of ≥140 mmHg or diastolic blood pressure (DBP) of ≥ 90mmHg].
• History of cerebrovascular accident.
• Major surgery or trauma within 28 days prior to first dose of investigational product and/or presence of any non-healing wound, fracture, or ulcer (catheter placement and similar procedures are not considered to be major surgery).
• Evidence of active bleeding or bleeding diathesis.
• Known endobronchial lesions and/or lesions infiltrating major pulmonary vessels that increase the risk of pulmonary hemorrhage.
• Recent hemoptysis (>=½ teaspoon of red blood within 8 weeks before first dose of study drug).
• Any serious and/or unstable pre-existing medical, psychiatric, or other condition that could interfere with patient's safety, provision of informed consent, or compliance to study procedures.
• Unable or unwilling to discontinue use of prohibited medications listed in the protocol for at least 14 days or 5 half-lives of a drug (whichever is longer) prior to the first dose of study drug and for the duration of the study.
• Treatment with any of the following anti-cancer therapies:

Radiation therapy, surgery or tumor embolization within 28 days prior to the first dose of pazoapnib or Chemotherapy, immunotherapy, biologic therapy, investigational therapy or hormonal therapy within 14 days or five half-lives of a drug (whichever is longer) prior to the first dose of pazopanib

• Administration of any non-oncologic drug within 30 days or 5 half-lives (whichever is longer) prior to receiving the first dose of study treatment.
• Ongoing toxicity from prior anti-cancer therapy that is >Grade 1 (except anemia, see Table 1 above) and/or that is progressing in severity, except alopecia.
• Have a known immediate or delayed hypersensitivity reaction or idiosyncrasy to drugs chemically related to pazopanib.