Understanding Adenocarcinoma
Adenocarcinoma refers specifically to cancers that affect cells that are glandular in nature. “Adeno-” is the prefix for “gland” while “-carcinoma” is a term used to describe cancers that begin in the skin or in tissues that line the organs.
Adenocarcinomas develop because the colon is made up of a vast network of glands, which serve two key functions:
To absorb water from the feces back into the bloodTo secrete mucus into the colon to lubricate feces as they are expelled from the body
If these cells are unable to produce ample mucus, the lining of the colon can become damaged by friction and scraping from unlubricated stools passing through. Over time, this can lead to damage on the genetic level, causing the cells to multiply abnormally without any means to prevent or temper replication. This factor triggers the formation of adenocarcinoma.
Definition of Mucinous Adenocarcinoma
MAC tumors in the colon originate from the same genetic cause as adenocarcinoma. However, there are important differences. Instead of producing less mucus, MAC cause the colon to produce far more mucus.
With MAC, your body forms tumors comprised of at least 50% mucin. Mucin is not mucus per se, but rather it is the glycoprotein component that makes up mucus along with other bodily fluids (such as saliva and breast milk). It is this mucinous component that many believe helps a tumor spread easily as it seeps beyond the walls of the tumor to the adjacent tissue.
Because of this ability to seep, MAC has long been considered a more aggressive form of adenocarcinoma.
Risk Factors
MAC has distinct characteristics that make it different from other types of colon cancer. Some of the factors that are closely associated with its development are similar to risk factors for other types of cancer. Some are different. Risk factors for MAC include:
Younger age Being female History of inflammatory bowel diseases, such as Crohn’s disease or ulcerative colitis History of pelvic or abdominal radiation therapy
How Mucinous Adenocarcinoma Is Diagnosed
MAC is diagnosed via a colonoscopy when polyps are biopsied or removed and later examined under a microscope. If a sample consists of at least 50% mucin, it’s considered mucinous adenocarcinoma, which can require the entire tumor to be removed and studied.
The pathologist who studies the tumor will check the depth of invasion, looking at whether the tumor has spread to layers beyond the mucosa, and if so, how deep beyond it. The cancer is assigned a stage based on the TNM staging system, which grades the tumor (T), nodal (N), and metastatic (M) qualities.
T1 – Tumor is in the layer just below the mucosa on the inner surface of the colonT2 – Tumor has spread two layers below the mucosa to the muscularis propria. T3 – Tumor has invaded the muscular wall and the fat near the outer surface of the colon. T4 – Tumor has spread out to the tissue on the outer surface of the colon or to surrounding organs.
Tumors are assigned a nodal stage to indicate if they have spread to the lymph nodes and a metastatic stage based on whether they have spread to distant areas beyond the colon.
MAC is usually diagnosed in the more advanced stages of the disease. This is due, in part, to the fact that mucinous tumors have a far softer consistency than “standard” tumors and are often not detected until they’re larger and more pronounced.
Even when detected early, the tumor’s poorly defined shape and border make it hard for even experienced pathologists to properly stage.
Mucinous Adenocarcinoma Treatment
Researchers have long believed that the mucinous component helps a tumor spread quickly and makes it far less receptive to treatment than non-mucinous cancer of the colon. However, both of these beliefs have been challenged and are hotly debated among researchers, some of whom hypothesize that it is not the speed of development but rather the stage when the tumor is found that leads to poorer outcomes.
Currently, mucinous colorectal adenocarcinoma is treated with the same approaches used for other types of colon cancer. These include:
Surgery Radiation Targeted therapy Immunotherapy Chemotherapy
However, chemotherapy may not be as effective for MAC as for other forms of colon cancer.
The excess production of mucin creates a barrier that may, in fact, prevent chemotherapy medications from effectively penetrating MAC cancer cells. In short, the chemo may not be able to get where it needs to go.
A Word From Verywell
MAC has distinct characteristics that make it harder to diagnose and make these tumors more likely to be found late. This may lead to shorter survival times. Thus, it is very important to work with your doctor if you suspect you might be at risk for MAC.Even if an initial colonoscopy finds no cancer, do not hesitate to request further investigation if symptoms persist or worsen. Alternately, you can seek a second opinion from a colorectal specialist experienced in MAC and signet-ring cell carcinoma.
