Adenoid Cystic Carcinoma

Epidemiology

Adenoid cystic carcinoma (ACC) is a malignant epithelial tumor that can arise from major or minor salivary glands. These are uncommon tumors that constitute about 4% of all parotid tumors and approximately 15% of parotid malignancies. They most commonly present between 40 and 60 years of age. Males and females are equally affected.

Clinical Findings

These tumors typically present as a slow-growing mass in the parotid region that may occasionally be painful. Perineural invasion is the hallmark of this malignancy. ACC is the most common malignancy of the parotid gland to be associated with facial nerve weakness. This is due to the propensity of this tumor to invade nerves.

Pathology

These tumors probably arise from the canaliculi and intercalated ducts of the peripheral duct system of the salivary glands. On gross examination, these tumors are typically unilobular and appear grayish white or yellowish white on cut section. The tumors are relatively circumscribed with little or no encapsulation. There are four main histologic patterns of ACC: cribriform (classic), tubuloglandular, solid, and cylindromatous (hyaline). Neural invasion is a constant histologic finding. Skip lesions where uninvolved segments of nerve may be interspersed between involved segments also characterize these tumors. As a result, “clear” surgical margins play a less important prognostic role when compared with other malignancies.