Salivary Gland Neoplasms: Adenoid Cystic Carcinoma

• Adenoid cystic carcinoma is the second most common salivary gland malignancy overall, but is the most common in the submandibular, sublingual and minor salivary glands.
  
• It occurs equally in men and women, peaks in the 5th decade of life and is more common in Caucasians.

Clinical presentation is often an asymptomatic mass, however, this tumor is more likely than others to present with pain or paresthesias. Facial paralysis remains rare, but again, may be seen more frequently with adenoid cystic than with other tumors. Minor salivary gland involvement is characterized by a submucosal mass with or without pain and ulceration.

Gross appearance is typically a well defined but not encapsulated mass that can be seen infiltrating surrounding normal tissue. Despite their name, these are solid tumors that rarely display obvious cystic spaces on the cut surface.

Microscopic appearance is described as cribriform, tubular or solid. The cribriform pattern is the most common and most easily recognizable. It is often referred to as the “swiss cheese” pattern. Tumor cells are arranged in nests around cylindrical spaces that may contain a mucinous or hyalinized material. Cells that are arranged in layers and form ductal structures characterize the tubular pattern. The solid pattern contains sheets of tumor cells with no intervening spaces.

Current treatment recommendations for adenoid cystic carcinoma include complete surgical resection and postoperative radiation therapy. Because of the propensity for this tumor to demonstrate perineural invasion, sacrifice of the facial nerve may be necessary for tumor eradication. Elective neck dissection is usually not indicated because this tumor rarely involves the cervical lymph nodes. Even with seemingly adequate treatment, local recurrence of adenoid cystic carcinoma is unfortunately not uncommon.

Tumor recurrence rates vary in the literature but reportedly can be as high as 42%. Another problem with this tumor is its propensity for distant metastasis, the most common site being the lung. Both local recurrence and distant metastasis can develop many years after initial treatment and multiple recurrences in the same patient have been reported. Although the prognosis for complete cure is poor, the course of disease is often indolent and patients with adenoid cystic carcinoma may survive for many years before eventually succumbing to the disease.

Category: Pathology Notes