Adenoidcystic Carcinoma

Epidemiology

Primary tumors of the parapharyngeal space are rare and they usually arise from minor salivary glands. The hard palate has the highest concentration of minor salivary glands in the upper aerodigestive tract, and it is the most common site for benign and malignant minor salivary gland tumors. Minor salivary glands are also found in the tongue, hard palate, lips, and cheeks, but occasionally these tumors are seen in the parapharyngeal space. About half of all minor salivary gland tumors are malignant and two thirds of them are adenoid cystic carcinoma.

Clinical Findings

The parapharyngeal space is large and deep-seated. Most tumors present when they have reached a large size. These tumors produce pain when they erode other structures such as bone. Adenoid cystic carcinoma with perineural spread may also present with pain.

Pathology

Adenoid cystic carcinomas most commonly arise submucosally and often presents as advanced disease. Histologically, adenoid cystic carcinomas are low-grade malignancies but their biological behavior resembles that of high-grade malignancies. There is a high tendency for recurrence and a 50% chance of distal metastasis. These tumors have a high propensity for perineural infiltration and this mode of spread may be seen in 50% of patients.