Identification of tophi indicates a definitive diagnosis of gout. However, recently they are rarely encountered. Tophi are most often seen in tissues that have a poor blood supply and low temperature, such as the ear helix and first MP joint. The nodules are yellowish-white, and non-tender, and range in size from 1 mm to 7 cm. Aspiration yields a chalky-like material that appears as needle-like crystals under light microscopy. In more advanced cases, tophi have a "punched-out" appearance with an "overhanging" margin on X-ray images. Differential diagnoses include rheumatoid nodules, xanthoma tuberosa, and CPPD crystal deposition diseases. Tophi respond well to anti-hyperuricemic therapy, during which they gradually decrease in size. However, a huge nodule may need to be surgically removed.