One thinks of the parotid gland as lying external or superficial to the ascending ramus of the mandible. About 80% to 85% of the parotid does in fact lie in such a position. There is a small portion, however, which hooks around the posterior margin of the mandible and extends for variable distances medial to this structure. Tumors arising from this retromandibular portion present an entirely different problem, from the point of view of both symptoms and management, from that which is encountered in the classic and better-known tumor arising from the superficial portion of the gland.
Judged from the clinical histories of patients with this tumor, their therapy has been the source of considerable perplexity on the part of the physicians to whom they have applied for help. Their occurence in such an anatomically inaccessible area has led some to declare such growths as "inoperable" or to recommend x-ray
MORFIT HM. Retromandibular Parotid TumorsTheir Surgical Treatment and Mode of Origin. AMA Arch Surg. 1955;70(6):906-913. doi:10.1001/archsurg.1955.01270120114013