Pazopanib Hydrochloride in Treating Patients With Advanced Angiosarcoma

Inclusion Criteria: * Subjects must provide written informed consent and Health Insurance Portability and Accountability Act (HIPAA) consent prior to performance of study-specific procedures or assessments and must be willing to comply with treatment and follow up * Note: informed consent may be obtained prior to start of the specified screening window * Note: procedures conducted as part of the subject's routine clinical management (e.g., blood count, imaging study such as bone scan) and obtained prior to signing of informed consent may be utilized for screening or baseline purposes provided these procedures are conducted as specified in the protocol * Histologically or cytologically proven diagnosis of advanced stage angiosarcoma that is not amenable to treatment with curative intent; specify site of origin as cutaneous vs. non-cutaneous * Eastern Cooperative Oncology Group (ECOG) performance status of =\< 2 * Must have measurable disease per Response Evaluation Criteria In Solid Tumors (RECIST) 1.1 or cutaneous disease amenable to serial measurements should be present; a measurable lesion is defined as a lesion that can be accurately measured in at least one dimension with the longest diameter \>= 10 mm with computed tomography (CT) scan; lesions that have been treated with therapeutic intent will be considered measurable if they have increased in size by more than 20% * Absolute neutrophil count (ANC) \>= 1.5 X 10\^9/L * Hemoglobin \>= 9 g/dL (5.6 mmol/L) * Platelet…