Tumors are abnormal lumps or bumps. Sometimes simply called a "mass," a tumor isn't necessarily malignant. Most hand tumors are actually benign (non-cancerous). Regardless of the cause, any lump or bump on your hand can be considered a tumor.
They can appear on the skin, such as a mole or a wart, or they can appear beneath the skin in the soft tissues or bone. There are many different tissue types in the hand (e.g. skin, tendon, fat, ligaments, bone, etc) so there are also many different types of tumors that can appear on the hands.
Tumors that appear on the hands include ganglion cysts, lipomas, neuromas, nerve sheath tumors, fibromas, glomus tumors, and others. The most effective treatment for hand tumors is surgical excision, combined with analysis of the tumor to determine its type.