Malignant Salivary Gland Tumors

Mucoepidermoid carcinoma

Mucoepidermoid carcinomas comprises about 30% of salivary gland malignancies. They are located most commonly in the parotid, and of parotid malignancies, they represent the most common malignancy. They are also the most common pediatric salivary tumor. Their appearance is extremely variable as the neoplasm can vary from high to low grade. The higher grade tumors tend to be extremely aggressive and infiltrating, whereas the low grade tumors may be well encapsulated and appear similar to benign lesions, such as a pleomorphic adenoma or a Warthin's tumor. The prognosis varies with the grade of the tumor.

Adenoid cystic carcinoma

The adenoid cystic carcinomas are the most common salivary tumor of the minor salivary glands and also of the submandibular and sublingual glands. They tend to be slow growing, but extremely persistent. They are known to have a high propensity for perineural spread, and one should look very carefully for signs of perineural spread along the courses of the facial nerve, as well as the third and second divisions of the 5th cranial nerve, particularly on follow-up examinations for known adenoid cystic carcinoma.

Squamous cell carcinoma

Squamous cell carcinoma can be found in the salivary glands, often as the result of direct spread from adjacent mucosal neoplasia or from metastasis to lymph nodes in the parotid or submandibular spaces. Therefore, one needs to search for a primary tumor whenever there is a diagnosis of squamous cell cancer in a salivary gland. Infrequently, squamous cell cancer can arise denovo, probably as the result of metaplasia of ductal columnar epithelium within the salivary gland. On imaging, these neoplasms tend to be hypointense on T2, but they do enhance on T1 weighted postgadolinium images with fat suppression.

Adenocarcinoma, expleomorphic carcinoma

Less commonly, adenocarcinoma involves the glandular tissue of the salivary glands, and it usually carries a bad prognosis. The signal intensity tends to be variable depending on whether the nature of the tumor is solid, mucinous, or cystic. Carcinoma expleomorphic adenoma may be the result of a pleomorphic adenoma that degenerates into a carcinoma. It is estimated that perhaps 20% of pleomorphic adenomas can do this. These malignancies to be very aggressive neoplasms with metastasis to the lungs and adjacent lymph nodes, in addition to very rapid growth of the primary tumor.

Lymphoma

Non-Hodgkin's lymphoma can affect almost any organ in the head and neck and the salivary glands are not immune. These tumors tend to be quite bulky and are often associated with large bulky homogeneous lymph nodes. They can exhibit very rapid enlargement.

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