Dear Alpeus, When a single lump is under 5 cm, not under the fascia, not painful, not increasing in size, it can be observed or excised and sent for tissue examination. If bigger, or with the worrisome features of growth, location under the fascia, over 5 cm, or painful, it should have a diagnostic MRI before excision. MRI is able to pick up features of a sarcoma and when consistent with a benign lipoma, makes the chance of being a sarcoma perhaps under 2%. The lipomas that can change to liposarcoma appear to be the larger ones, 10 cm or larger, and we always get an MRI for those. It is inadvisable to excise a large lump surgically, over 5 cm, without an MRI, as lumps that are over 5 cm, if they are liposarcoma, have metastases in the skin that may not be removed with excision of the lump.