Adenoid cystic carcinoma

December 31, 2014

Synonyms

Overview

Adenoid cystic carcinoma is a rare form of adenocarcinoma, which is cancer that begins in gladular tissues. ACC most commonly arises in the head and neck, in various parts of the major and minor salivary glands including the palate, nasopharynx, lining of the mouth, voice box (larynx) or windpipe (trachea). It can also occur in the breast, uterus, or other locations in the body. Early symptoms depend on the tumor's location and may include lumps under the lining of the mouth or facial skin; numbness in the mouth or face; difficulty swallowing; hoarseness; pain; or paralysis of a facial nerve. ACC often has long periods with no growth followed by growth spurts; however, it can be aggressive in some people. ACC spreads along nerves or through the bloodstream, and only spreads to the lymph nodes in about 5-10% of cases. The cause of ACC is currently unknown. Treatment depends on many factors and may include surgery, radiation, and/or chemotherapy.

Symptoms

These depend largely on the site of origin of the tumor. Early lesions of the salivary glands present as painless masses of the mouth or face, usually growing slowly. Advanced tumors may present with pain and/or nerve paralysis, for this neoplasm has a propensity to invade peripheral nerves. Tumors of the lacrimal gland may present as proptosis and changes in vision. ACC arising in the tracheobronchial tree may present with respiratory symptoms, while tumors arising in the larynx may lead to changes in speech.

Causes

The underlying cause of adenoid cystic carcinoma (ACC) is not yet known, and no strong genetic or environmental risk factors specific to ACC have been identified. Researchers believe that a combination of various genetic and environmental factors probably interact to ultimately cause a person to develop specific types of cancers. There is ongoing research to learn more about the many factors that contribute to the development of cancer.

Cancer is at least partly due to acquired (not inherited) damage or changes to the DNA in certain cells. For example, various studies have shown that chromosomal abnormalities and genetic deletions are present in samples of ACC. However, these genetic abnormalities are present only in the cancer cells, not in the cells with the genetic material that is passed on to offspring (the egg and sperm cells).

While the underlying cause of adenoid cystic carcinoma (ACC) is not known, no strong genetic risk factors have been identified.

Diagnosis

The diagnosis is made by histologic analysis of a biopsy or resection specimen of a tumor mass. There are three major variant histologic growth patterns of ACC: cribriform, tubular and solid. The solid pattern is associated with a more aggressive disease course. There are no serum markers for this neoplasm. Recurrences are usually identified by radiographic imaging techniques, such as computed tomography.

Treatment

Primary treatment for this cancer, regardless of body site, is surgical removal with clean margins. This surgery can prove challenging in the head and neck region due to this tumour's tendency spread along nerve tracts. Adjuvant or palliative radiotherapy is commonly given following surgery. In some cases surgery is not an reasonable option, however radiation used alone may provide an effective treatment. Neutron therapy has been shown to be superior for some types of cancer including adenoid cystic carcinoma of the head and neck. Chemotherapy is used for metastatic disease. Chemotherapy is considered on a case by case basis, as there is limited trial data on the positive effects of chemotherapy. Clinical studies are ongoing, however.