Intraoral adenoid cystic carcinoma: is the presence of perineural invasion associated with the size of the primary tumour, local extension, surgical margins, distant metastases, and outcome?

Adenoid cystic carcinoma is the most common malignancy of the minor salivary glands, and its biological behaviour is characterised by slow and indolent growth; rare involvement of regional lymph nodes; a high propensity for perineural invasion; multiple or delayed recurrences, or both; and a high incidence of distant metastases. Our aim was to find out the relation between the presence of perineural invasion and these factors. Between 1 January 1984 and 1 May 2008, 26 cases of adenoid cystic carcinoma of the intraoral salivary glands, which had initially been treated surgically, were reviewed retrospectively. The most common site was the palate, and perineural invasion was reported in 13 of the 26 resected specimens. There was no significant association between it and the size of the primary tumour (OR=1.0; p=1.00), invasion of the surgical margins (OR=2.08; p=0.4), the presence of distant metastases (OR=3.43; p=0.197), or local control (p=0.76). It was exclusively present in patients with local extension, and was significantly associated with outcome (p=0.04). Resection with clear margins is the gold standard of care for patients with intraoral adenoid cystic carcinoma, and the role of adjuvant irradiation remains controversial. Given its paradoxical and complex biological behaviour, large studies with long term follow-up are needed to define the clinicopathological and immunohistochemical variables associated with outcome, as well as the optimal treatment.