Any abnormal lump or bump (or mass) can be called a tumor, but this does not mean it is cancer. The vast majority of lumps and bumps in the hand are benign (non-cancerous). Tumors can occur in the skin, soft tissues under the skin or in the bone. The most common cause of tumors in the hand are ganglion cysts (See Ganglion Cyst). Treatment of hand masses can range from observation to surgical excision.