High-grade transformation of adenoid cystic carcinoma of parotid gland with isolated intratemporal facial nerve involvement: a case report and literature review

Abstract

Abstract Background High-grade transformation Adenoid cystic carcinoma (HGT-AdCC) of the parotid gland is a rare transformation noted in slow growing low grade AdCC. Perineural invasion and spread is an important feature of this tumor. Temporal bone involvement is rare. A total of only 10 cases of HGT-AdCC in parotid gland has been reported in literature so far predominantly in the elderly with peak incidence in 5th–6th decade. Case presentation We present a young lady of HGT-AdCC of right parotid gland with temporal bone involvement in the form of isolated perineural invasion (PNI) of facial nerve till the tympanic segment. She underwent right radical parotidectomy with modified radical neck dissection with modified lateral temporal bone resection and pectoralis major myocutaneous flap reconstruction. Histopathological examination revealed both low- and high-grade areas. Sections from facial nerve showed tumor invasion. Conclusion The radiological features of isolated perineural spread in intratympanic part of facial nerve can be easily missed if not specifically looked for. Every attempt should be made preoperatively and intraoperatively to determine the complete extent of the tumor for adequate disease clearance. A combined clinico-radiological approach aided by histopathology examination helps in early detection of this carcinoma and in better patient management.