Signet Ring Adenocarcinoma of the Appendix
(Signet Ring Cell Carcinoma)
Signet Ring Adenocarcinoma, also commonly called Signet Ring Cell Carcinoma, receives its name from the fact that when looking at the cell under a microscope, the cell is so full of mucous that the nucleus of the cell (which would normally be near the cell's center), is pushed to the edges, or periphery, of the cell. This makes the cell look like signet ring jewelry under a microscope. The signet ring cell type can occur in several different cancers. It is most commonly found in cancer of the lining of the stomach, but can also develop in the bowel, breast, pancreas, bladder, prostate, appendix or lung.
Signet ring cell is a rare type of cancer, and is the rarest of the appendiceal cancers. In the 25 years between 1973 and 1998 there were only 70 reported cases of signet ring appendix cancer in the USA. In one published medical study, 75% of cases of signet ring appendiceal cancer had already metastasized to adjacent organs, lymph nodes or to the peritoneal cavity on discovery. Signet ring is considered a high-grade, or aggressive, type of cancer.
As with other appendiceal cancers, signet ring can present as appendicitis or a perforated (ruptured) appendix. It may also present as an ovarian mass in females as it commonly metastasizes to the ovary. If extensive metastasis to the peritoneal cavity has occurred, it may present with bowel obstruction, abdominal pain or increased abdominal girth and bloating related to ascites. Signet ring adenocarcinoma is frequently in late stages of the disease when it is discovered. It can also progress rapidly.
Treatment: Treatment is the same as it would be for colonic-type adenocarcinoma:
Appendectomy with right hemicolectomy. Conflicting views in medical literature in regards to prophylactic removal of ovaries and fallopian tubes as this is commonly a site of metastasis.
In some literature intraperitoneal chemotherapy is recommended in addition to the right hemicolectomy even without peritoneal surface malignancies, especially for intermediate and high-grade tumors or in cases of appendiceal perforation.
Cytoreduction surgery and hyperthermic intraperitoneal chemotherapy are indicated for peritoneal metastasis/peritoneal carcinomatosis (tumors that have metastasized into the abdominal cavity)
Treatment with systemic chemotherapy commonly used to treat colon cancer is also used to treat signet ring appendiceal cancer. Formal studies have not been done to demonstrate the advantage of this chemotherapy for appendiceal adenocarcinoma due to the rarity of the disease, but based on the similarities between adenocarcinoma in colon cancer and appendiceal adenocarcinoma, a benefit is assumed. Some of the chemotherapy drugs commonly used are 5-FU, leucovoran, oxaliplatin and irinotecan. Avastin is also sometimes added. Avastin is not a chemotherapy drug, it is a monoclonal antibody that is anti-angiogenic; meaning it interferes with the growth of new blood vessels which provide nutrients to the tumor.
Mean age at discovery 58 years old, slightly more common in females
Signet ring adenocarcinoma has a poorer prognosis than the other varieties of appendiceal cancer. It is felt to be more aggressive and more resistant to chemotherapy than other cell types and is more likely to have metastasized on discovery. In some research 5 year survival is documented at 15-19%.