Parotid glands are located in front of the ear and create saliva. These are the glands that when infected with the mumps virus give patient the typical swollen face associated with mumps. It is not 
unusual for a deep lobe cryptic cancer of the parotid gland to present with slow progressive paralysis of the face. Unlike the facial paralysis associated with the Bell’s palsy, this paralysis is very slow in onset and usually starts with one or more branches of the nerve before it spreads to the entire nerve. For this reason, any facial paralysis that starts slowly and continues to progress over weeks and months is by definition not Bell’s palsy and warrants further workup.
Depending on the type of tumor, the treatment is usually surgery, graft of the involved facial nerve with other nerves, and possibly radiation. The prognosis is highly variable and depends on the type of tumor and its degree of extension into neighboring tissue as well as along the facial nerve. As one can see in this image the tumor could use the facial nerve as a path of extension all the way to the brain stem. Image courtesy of Dr. Robert Jackler, used with permission.