Why do your feet increase in size with carcinoid carcinoma?

Hormones: A carcinoid tumor is made of hormone-producing cells. Some hormones directly cause vasodilation (like the redness of your skin when you're in a hot-tub) which cause your feet to swell. Other hormones can damage your heart valves, which can indirectly cause your feet to swell. Carcinoid tumors don't make your feet actually grow to my knowledge, but they can get quite swollen.

Specific hormone: Growth hormone, or growth hormone like factors or somatomedins, can be produced by neuroendocrine tumors, of which carcinoid is considered the most common. Growth hormone results in growth of the feet, hands, face (specifically jaw and forehead). It is important to know that your tumor was producing a growth hormone like substance.