Liposarcoma. Section through a gross specimen of cancerous fat cells. The cells have an irregular shape and, unlike healthy fat cells, are not uniformly yellow. This is a liposarcoma, a malignant (cancerous) tumour of adipose (fat) cells. It is the most common soft tissue cancer in adults, mostly affecting those over 50 years of age. The tumours, which present as a localised swelling, are most common in the deep soft tissue of the trunk and lower limbs. Treatment is with surgical removal of the tumour, often combined with radiation therapy and chemotherapy.