Tumors of the appendix can be divided into two major groups:

Carcinoid Tumors

Carcinoid tumors are the most common form, representing about half of all appendix tumor cases. These tumors are more common in women, and generally occur in the fourth decade of life. About two-thirds of carcinoid tumors are found in the tip of the appendix, where they do not obstruct the opening between the appendix and colon.

In the majority of cases, carcinoid tumors are small (less than two centimeters) and have a very low risk of spread to nearby lymph nodes. Appendectomy (removal of the appendix) is adequate treatment in these cases. Larger tumors have a slightly higher risk of metastasizing to surrounding lymph nodes and the liver. Removal of the right colon and regional lymph nodes is recommended.

More than 85% of patients with carcinoid tumors of the appendix (even with regional metastases) have a five-year survival rate.

Most patients have no symptoms. However, some signs may include:

• Acute appendicitis: most cases are discovered during surgery for appendicitis
• Carcinoid syndrome (if spread to liver): flushing, shortness of breath, diarrhea, heart valve disease on the right side

Non-Carcinoid Tumors

Non-carcinoid tumors of the appendix originate from the epithelial cells lining the inside of the appendix. Most of the cells creating these tumors produce a gelatinous material known as mucin. Due to the anatomic structure of the appendix and the mucin production of these tumors, patients with non-carcinoid tumors of the appendix are at risk for spread of tumor cells and mucin within the abdominal cavity. If left untreated, both tumor cells and mucin can accumulate over time and lead to life-threatening bowel obstruction and cachexia (weight loss, muscle atrophy, significant loss of appetite, fatigue). Prognosis and treatment for these tumors depend on a number of patient and tumor-related factors.

Pseudomyxoma peritonei (PMP) is defined by the presence of acellular (i.e., few, if any, tumor cells) mucin within the abdominal cavity. The most common presentation of PMP is a mucin-producing tumor of the appendix whose cells have spread outside the appendix and into the abdominal cavity. The resulting tumor, which looks like orange jelly, can get as large as 20-30 pounds.

There are no PMP-specific symptoms, but some of the more frequent presenting signs include:  

• Increase in abdomen size/girth
• Vague abdominal discomfort; persistent discomfort in the lower right abdomen
• Pelvic discomfort
• New hernias
• Bowel obstruction
• Ovarian masses

Adenocarcinoid tumors, also known as goblet cell carcinomas, have characteristics similar to both carcinoid and adenocarcinoma tumors of the appendix. Most patients are diagnosed in their 50s. The prognosis for these tumors is slightly poorer than that of carcinoid tumors, with an overall five year survival rate of 78%. The main presenting symptom is acute or chronic abdominal pain.