Lipoma tumour, light micrograph. A lipoma is a benign (non-cancerous) tumour of fat cells (adipocytes, red). Tumours are slow growing and can develop anywhere where there is fat tissue. Often there is no known cause of lipoma growth, but injuries or genetic factors can play a part. Lipomas are generally painless and cause no symptoms. However, their growth may compress nearby tissues, leading to pain or impaired function. In that case, the lipoma is removed surgically.