Swelling in the Floor of the Mouth: Adenoid Cystic Carcinoma

Abstract

Adenoid cystic carcinoma (ACC) is a rare form of adenocarcinoma that begins in glandular tissues with highest prevalence in patients in their sixth decade of life. It occurs most frequently in the major and minor salivary glands of the head and neck. Clinically, ACC often manifests as a swelling in the floor of the mouth and may have pain and/or numbness as accompanying symptoms. When it occurs in the parotid gland, facial nerve palsy is a pathognomonic clinical feature in most patients. ACC often spreads along the nerves and sometimes through the bloodstream. Only a small fraction of cases spread along the lymphatics. The exact aetiological factors for ACC are still unknown, and there is no evidence of hereditary basis for occurrence. Typically, an ACC would demonstrate significant characteristic features in MRI. They often appear hypo to isointense in T1 window, while it tends to be slightly hyperintense in T2 window which increases significantly with higher grades of tumour. Histopathologically, ACC may manifest as tubular, cribriform, or solid types whereby those with more solid components end up with poorer prognosis. Perineural invasion is an unequivocal feature in adenoid cystic carcinoma. Radical excision is the mainstay of treatment modality with or without post-operative radiotherapy/chemotherapy.