A nodule is a growth of abnormal tissue. Nodules can develop just below the skin. They can also develop in deeper skin tissues or internal organs. Dermatologists use nodules as a general term to describe any lump underneath the skin that's at least 1 centimeter in size. It's not a specific diagnosis. Endophytic tumors were defined when the tumor growth appeared prin- cipally to be below the surface epithelium. Exophytic nodule refers to a nodule that sticks out of the normal thyroid boundary/outline.