The features of subnail melanoma include etiologic features, clinical manifestation features, pathological features and other aspects. 1. Etiologic features: its onset is closely related to local nevi, strong ultraviolet irradiation, local trauma and irritation, repeated nail extraction, repeated incision or excision, and so on. 2. Clinical manifestations: its typical clinical manifestations are black-brown plaques under the nails or longitudinal black lines under the nails, and in severe cases, there may be swelling and pain in the extremities, bloody oozing under the nails, peeling off of the nail plate, ulceration of the nail bed and the surrounding tissues, long-lasting ulceration, and growth of black-brown and brittle granulation tissues. 3. Pathological features: malignant subnail melanoma has sarcomatoid, epithelioid, pseudo-glandular cell morphology under the microscope, which can be accompanied by fibrous mesenchymal reaction, and most of the abnormalities of HMB45, Ki67 and cyclinD1 exist. Most subnail melanomas are malignant tumors. When subnail melanoma is suspected or the above symptoms occur, timely consultation is recommended.