The type of cells involved and how the cells appear under a microscope are used to classify the appendix cancer types. The type of cells is named by their behaviors, like the likelihood of spreading to other regions of the body, pace of development, and the ability to be eliminated surgically.

Two main types of appendix cancer- carcinoid tumors and carcinomas

(A) NEUROENDOCRINE TUMOR

These are the most prevalent appendix cancers, accounting for almost half of all cases. They are more common among women in their forties. A neuroendocrine tumor (NET) begins in hormone-producing cells, which are found in small quantities in nearly every organ of the body. It is also known as a carcinoid tumor. A neuroendocrine tumor most commonly begins in the gastrointestinal system or the lungs, although it can also develop in the pancreas, testicles, or ovaries. These tumors typically develop slowly and are categorized as low-grade tumors, but they can grow quickly in certain circumstances. The small intestine, rectum, and appendix are the most common sites for the development of NET. Multiple tumors can develop at the same time. The most favorable location for an appendix neuroendocrine tumor is the tip of the appendix. Neuroendocrine tumors make up around half of all appendix tumors. Appendix cancer generally does not produce symptoms until it has spread to other organs, and it often remains unnoticed until it is discovered during a routine checkup or surgery. An appendix neuroendocrine tumor that remains limited to the region where it began has a good chance of being treated successfully with surgery.

(B) CARCINOMAS

The most frequent kind of cancer is carcinoma. It starts in the skin's epithelial tissue or the tissue that lines internal organs such as the appendix, liver, and kidneys. Carcinomas can either spread to other areas of the body or be confined to one region.

Carcinomas of the appendix are as follows:-

(1) Appendiceal mucoceles:-

Mucoceles are mucous-filled swellings or sacs caused by the bulge of the appendix wall. A mucocele can be caused by a variety of benign to malignant diseases in the appendix. Mucinous cystadenomas and mucinous cystadenocarcinomas are two such conditions. Mucinous cystadenomas are identical to adenomatous polyps developed in the colon and are benign hence, do not spread. They can be fully eliminated with surgery if they are confined in the appendix. If the appendix ruptures, however, the cells may spread throughout the body and continue to exude a jelly-like material called mucin into the belly. Mucin buildup can cause stomach discomfort, bloating, and bowel dysfunction, including bowel obstruction (blockage). Mucinous cystadenocarcinomas can have similar effects as mucin in the abdomen, but they are malignant, meaning they can spread to different parts of the body.

(2) Goblet cell carcinoid:-

Also known as adenocarcinoid tumors. These are less frequent tumors that are not carcinoid tumors or NETs, despite their names. Goblet cell carcinoid (GCC) tumors are a unique and distinct tumor form that arises mostly in the appendix, with only a few instances occurring elsewhere. Adenocarcinoid, mucinous carcinoid, crypt cell carcinoma, and mucin-producing neuroendocrine tumor are the other names used to describe this entity, but none is universally accepted. Dual neuroendocrine and mucinous differentiation is considered to give rise to the tumor from pluripotent intestinal epithelial crypt-base stem cells. Acute appendicitis is the most frequent clinical manifestation, followed by abdominal pain and a mass.

The histologic characteristic of this entity is the appearance of clusters of goblet cells in the lamina propria or submucosa stain for many neuroendocrine markers, though the intensity is often uneven. Although atypia is generally mild, carcinomatous growth patterns can be detected. These might be signet ring cells or adenocarcinomas with poor differentiation. Overall survival is 76 percent after five years. They behave and are treated in the same manner as mucinous adenocarcinoma.

(3) Signet-ring cell adenocarcinoma:-

The rarest of the appendiceal malignancies, signet ring cell carcinoma has a non-specific clinical presentation like the others. A right lower quadrant abdominal discomfort indistinguishable from acute appendicitis is the most prevalent sign of these tumors. Mucinous adenocarcinoma behaves and is treated similarly to goblet cell carcinoids. They are more aggressive than carcinoid tumors and more commonly affect people over the age of 50. At the time of diagnosis, metastases to neighboring organs, lymph nodes, or the peritoneal cavity are present in 93 percent of patients.

(4) Intestinal-type adenocarcinoma:-

It is also known as colonic-type adenocarcinoma. Appendix tumors account for around 10% of all appendix tumors and are generally located near the appendix's base. Its symptoms are like that of colorectal cancer. It typically goes undetected, and the diagnosis is commonly diagnosed during or after appendicitis surgery. Appendicitis is an inflammation of the appendix that causes stomach discomfort, swelling, nausea, vomiting, constipation or diarrhea, difficulty in passing gas, and a low temperature that appears after other symptoms.

(5) Paraganglioma:-

This is a rare tumor that arises from paraganglia cells, which are a collection of nerve tissue cells that remain in tiny deposits after fetal (pre-birth) development. Paraganglia can be seen in the head and neck region of the body, around the adrenal glands, blood arteries, and nerves. This form of tumor is typically benign, and it may frequently be effectively treated by surgical excision of the entire tumor.

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