Adenoid Cystic Carcinoma of the Gingiva: A Case Report and Literature Review.

[OBJECTIVES] Adenoid cystic carcinoma (ACC) is a commonly encountered salivary gland malignancy. However, it rarely occurs in the gingiva, an area generally thought to be devoid of minor salivary glands. We present a case occurring in this unusual site and review other reported cases.

[METHODS] A 56 year-old male presented with a right-sided mandibular toothache for 1 year and underwent dental extraction. Due to persistent pain, follow up examination revealed a large gingival lesion. A biopsy was positive for adenoid cystic carcinoma.

[RESULTS] The patient underwent a complete right segmental mandibulectomy and was reconstructed with a fibular osteocutaneous free flap. Three months postoperatively, during the planning for adjuvant radiation therapy, the patient developed pain in the left mandible. Imaging revealed extensive involvement of the left native mandible. Deep bone biopsies in several areas of the left mandible revealed ACC. He then underwent a complete left hemi-mandibulectomy and reconstruction with a fibular osteocutaneous free flap. Tensor fascia lata suspension slings were placed due to concern for an open mouth deformity attributable to disruption of bilateral masticator slings. He will undergo adjuvant radiation therapy. Our review of the literature revealed 50 cases of gingival ACC published since 1972. Disease recurrence and distant metastases were noted in several patients, occurring at the latest after 30 years follow-up.

[CONCLUSIONS] Given its indolent behavior, high proclivity for late recurrence and metastasis, and overall infrequency, ACC represents a pathology that requires early diagnosis and comprehensive long-term surveillance. While ACC is well described in oral cavity sites with high densities of minor salivary glands, it is not commonly seen in the gingiva. As such, gingival ACC may display a unique biological and/or clinical character. We offer the first literature review of this rare entity.