Well it sounds like you have done your homework. Salivary gland tumors are not rare, but they are more uncommon in the US than other oral cancers. They occur predominantly in the parotid area, and less frequently in the other salivary glands. They are seldom SCC (but can be), and are usually referred to as "mixed" tumors as it takes a histological examination to determine exactly what's what. Technically they are usually adenoid cystic carcinomas, or mucoepidermoid carcinomas. It is rare for a patient to present with two different oral cancers, but not unheard of. Tonsilar cancers are almost always SCC. All this is all academic to your friend, as the treatment protocols are the same regardless of the type of tumor. As with other oral cancers, salivary gland tumors favor the lungs as a site for distant metastasis, and a spiral CT scan should be done of the lungs early on to ensure that there is no involvement there. I hope for a complication free treatment period and rapid recovery for your friend.