Malignant Salivary Gland Tumors
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
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.
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.