Signet ring cell, or signet cell, colon cancer is an aggressive type of colon malignancy that accounts for less than 1% of colon tumors. The name "signet ring" refers to the resemblance of the cancer cell shape to that of the outline of a signet ring. Signet ring cancers are different from other types of colon cancer in a number of ways. One differentiating factor is the way in which signet ring cell cancers typically infiltrate the colon. Most colon cancers develop from pre-cancerous polyps (mushroom-type structures in the colon) that are readily diagnosed through routine screening such as colonoscopy. Either because they arise in small or 'flat' polyps that are difficult to detect during upon routine colonoscopy, or because this type of cancer grows more quickly than other types of colon cancer, these cancers are usually very advanced when patients are diagnosed.
Signet ring cancers also differ in the manner in which they spread from the colon to external organs. While many distant metastases of ordinary colon cancers occur in the liver, the signet ring cell tumor is frequently seen infiltrating the peritoneum, which is a membrane enclosing the organs of the abdomen (sometimes compared to an under filled balloon, through which the organs poke through like fists). This type of spread is marked with a distinctive growth pattern: the tumor grows in flat surfaces referred to as sheets. This presents numerous diagnostic difficulties, since such metastasis tends to be under-appreciated on imaging such as CAT and PET scans.
It has been concluded by a handful of research studies that chemotherapy has relatively poor curative efficacy in signet ring patients and that overall survival rates are lower in comparison with those with cancers of more typical pathology. This can be attributed largely to the fact that signet ring cancers are usually diagnosed during the late stages of the disease and that these tumors generally spread more aggressively than non-signet cancers. The small number of cases of signet ring colon cancer has precluded an exhaustive exploration of distinctive treatment methodologies for this type of malignancy. The currently accepted methodology in the colorectal oncology community is to treat signet cell colon tumors as a more aggressive version of non-signet cancers. For example, stage II signet ring colon cancer patients are treated as if they were typical stage III colon cancer patients.
If you are the child or a close relative of someone who has had signet ring carcinoma of the colon, it is important for you to have a conversation with your doctor about additional screenings. The rule of thumb for children of signet ring patients is to start getting colonoscopies 10 years before the parent was diagnosed. Because there is still so much research to be done, you should discuss having colonoscopies with a specialist who knows how to look for flat cancers. One technique, which is currently being actively investigated, is called Narrow-Band Imaging (NBI), uses a dark dye to help identify flat lesions. Even alerting your doctor to be extra vigilant in looking for flat cancers during your colonoscopy because of your family history is a step in the right direction.
For those diagnosed with signet ring colon cancers, as well as for their families, gathering information about the disease can be a tremendously exhausting and disheartening effort. The truth is that more research is needed in this specific area, and ongoing work is in its early stages. Historically, there have only been retrospective analyses, which aim at gathering statistical data on those who have been diagnosed and/or treated.
The Seidman Cancer Center of University Hospitals is currently working with the Bogomolnaya family to raise funds in order to investigate prevention and treatment techniques for signet ring colon cancers. You can make a big difference by contributing to this study. Please click here to make a tax deductible contribution.