Overview of Adenoid Cystic Carcinoma

Executive Summary

Adenoid cystic carcinoma (ACC) takes place in the salivary gland of the neck and head region. It is a rare type of adenocarcinoma which explains the growth of cancer cells in epithelial tissues. The cell shows slow growth because it is dangerous in nature. It spreads in other part of the body through the bloodstream or along the nerves, known as a perineural invasion. Adenoid carcinoma is an aggressive cancer hence it is complex to treat and cure it. The outcome of the diagnosis and treatment is unpredictable in this cancer. ACC has total three types of tumors, Cylindroma, Cribriform, and Solid. Surgery is the standard treatment that aims at removing the tumor from a specific region of the body. Experts also recommend postoperative radiotherapy and chemotherapy as it slows down tumor growth.

What is Adenoid Cystic Carcinoma

This cancer is the result of variations in the healthy cells, with uncontrollable growth, hence forming a mass of tumors in a specific region of the body. So, the cancer cells can be malignant or benign, depending on their extent of spread across the body. Adenoid cystic carcinoma (ACC) is the type of cancer developing in the salivary glands of the neck and head region.

It is the rare type of adenocarcinoma which describes cancerous growth within epithelial tissues. So, breast, skin, trachea, lacrimal gland, cervix, uterus, prostate etc. may get adenoid cystic carcinoma. 

The carcinoma is an unusual tumor which shows very slow growth but can be lethal. It is locally invasive cancer. It is capable of infiltrating the coatings or the sheaths, wrapping the nerve fibers or perineural spaces. Adenoid cystic carcinoma appears as abnormal cell cords surrounding or infiltrating the glandular structures and other ducts when observed under the microscope. Cells have cystic structures filled with mucous-like material. It comprises abnormal fibrous membranes hence it is known as hyaline membranes.

Nature

Therefore, it results in developing cancerous conditions commonly within the salivary glands, with cells secreting saliva. The glands are spread throughout the upper aerodigestive tract involving tissues and organs in the upper digestive tract of the mouth, lips, tongue, nose, throat, part of the windpipe and esophagus and the vocal cords.

Metastasis

Adenoid cystic carcinoma usually metastasizes to distant body sites instead of spreading to the nearby lymph nodes. Hence, it shows variations from other carcinomas concerned with the extent of its spreading. These cancerous growths have the chances of recurrence even after treatment and reappear within the site where the cancerous growth or tumor was first developed. The common region of metastasis of this carcinoma is the lungs and liver. And so, if it shows metastasis to the bones, it represents a poor prognosis. 

Salivary glands within the body are classified into two parts; minor salivary glands and major salivary glands. The growth of cancer cells begins in any region either in major or minor salivary glands.

 Minor salivary glands

It includes the following:

• The palate is the roof of the mouth. 
• The tongue base represents the back third of the tongue.
• The nasopharynx is an air passageway which is located at the upper part of the throat and behind the nose. 
• The larynx is the voice box.
• The mucus lining inside the mouth represents the inner lining of the mouth, having glands that secrete mucus.
• The trachea is also called the windpipe.

Adenoid Cystic Carcinoma (ADCC) tends to appear in any of the above-mentioned body areas.

Major salivary glands

It further includes the following:

• Parotoid glands are the most prominent salivary glands, located on either side of the face and in front of each ear.
• Sublingual glands are located under the tongue.
• Submandibular glands are located under the jawbone.

Adenoid cystic carcinoma shows metastasis through the bloodstream or the nerves. It is also known as a perineural invasion. Initially, it spreads to distant body parts, with lungs and liver known to be the most common organs. Approximately 5-10% metastasis takes place nearby lymph nodes.

Hence, adenocarcinoma shows no growth for an extended period, but a sudden spurt of growth may be observed. Adenoid carcinoma is aggressive while showing complexities in the course of treatment and cure with unpredictable outcomes.

Adenoid cystic carcinoma is classified as per its appearance under microscope. This classification further depends upon the histologic variations of the tumor ^​1​. The categories for the same are as follows:

• Cylindroma: It is a tumor with tube-shaped cells.
• Cribriform: It is a tumor appearing as Swiss cheese that present with a gap in between the cells.

Treatment

Surgery is considered as the primary and standard treatment for Adenoid Cystic Carcinoma. It removes the tumor and eliminate the growth of cancer cells ^​2​. The prevention of local recurrence also needs to be addressed. 

References