There are many kinds of cancers of the foot; some take the form of cysts and lesions, while others are more widespread.
Malignant melanoma is a skin cancer that is very curable if caught early. Although it makes up only 1 percent of skin cancers, malignant melanoma accounts for over 60 percent of skin cancer deaths. It is estimated that approximately 30% of melanomas occur in the lower extremities, and that 3% occur in the feet.
Neoplastic disorders, usually called tumors, are the result of abnormal growth of tissue and may be benign or malignant.
Osteochondromas are benign bone tumors under the toenail. They form in the bone beneath the toenail. An osteochrondroma accounts for about half of all benign bone tumors, occurring mostly in children and young adults. Unless they cause irritation to the surrounding tissue, they are generally not very painful. Sometimes, they can deform the toenail and cause an ingrown toenail. In some cases, they are removed surgically, but can recur even after the procedure.
A plantar fibroma is a benign tissue tumor or growth on the plantar, or bottom surface of the foot. Unlike plantar warts, which grow on the skin, these grow deep inside on a thick fibrous band called the plantar fascia. When non-surgical measures for treating plantar fibromas, such as orthotics, have failed to provide adequate relief of symptoms, surgical removal is a reasonable option.
Giant cell tumors are usually benign non-cancerous tumors of the tendon sheath. These masses are generally found on the toes, top of the foot or sides of the foot. They can also occur deep inside the foot. They are firm irregular masses that are commonly painful.