Introduction: Adenoid cystic carcinoma (ACC) is a rare, slow growing neoplasm accounting for 1–2% of head and neck malignancies, mainly affecting the salivary glands. There are no known risk factors. Presentation can be variable and histological diagnosis is required. Treatment requires surgical resection with adequate margins. It has propensity to spread perineurally and recur. Distant metastases, particularly to the lung and bone may occur. Adjuvant radiotherapy does not improve overall survival and there is conflicting information in the literature with regards to its control of local disease. Chemotherapy has not been found to be effective for local or distant disease.

Case: A thirty-four year old female was referred to the oral and maxillofacial surgery department with suspected pericoronitis which had not responded to a course of antibiotics. Clinical examination revealed an unerrupted wisdom tooth, with localized swelling of the overlying operculum and lingual mucosa. Orthopantogram showed a large radiolucency associated with the unerupted 3rd molar. Due to unusual presentation. CBCT was requested and demonstrated thinning of the lingual bone and bony expansion. An incisional biopsy showed ACC. CT showed the tumour arose from around the 3rd molar, perforating through the lingual plate and into the tail of the left sublingual gland. The patient underwent a left hemimandibulectomy, partial glossectomy, removal of sublingual gland and adjacent medial pterygoid muscle. Elective neck dissection was performed with the resulting defect reconstructed with a microvascular graft from the hip.

Conclusion: Thus case describes an unusual presentation of ACC which is a rare malignancy. It is slow growing but notorious for local recurrence and perineural spread. Adjuvant radiotherapy to the tumour site is recommended. Metastases can occur, despite adequate local control. Overall, prognosis is poor with staging being a significant factor. Unusual presentation of common conditions should arouse an index of suspicion.