Liposarcoma: A malignant tumor that arises in fat cells in deep soft tissue, such as that inside the thigh. Most frequent in middle-aged and older adults (age 40 and above), liposarcomas are the most common of all soft-tissue sarcomas. QUESTION What causes tooth decay? See Answer From Healthy Resources 10 Rheumatoid Arthritis SymptomsWhat Is Exocrine Pancreatic Insufficiency?Common Health Conditions Among Minorities Featured Centers Good and Bad Foods for PsoriasisVideo: Getting Personal on Life With MS Health Solutions From Our Sponsors Shot-Free MS Treatment Your Child and COVID-19