High-grade or aggressive neuroendocrine tumors are divided into a large cell and small cell tumors, which differ based on the appearance of the cells under a microscope. Both types of cancer are considered highly "undifferentiated," which essentially means that the cells appear very primitive relative to normal neuroendocrine cells and behave very aggressively.

In some ways, high-grade neuroendocrine tumors are similar to small cell lung cancer, and often respond to similar treatments, but are less likely to be associated with smoking than small cell lung cancers and are less likely to have metastases to bones and the brain.

Some studies have found that the tumors occur more commonly on the right side of the colon (ascending colon) whereas a recent study found that the most common location for these tumors was the rectum and sigmoid colon.³



Colon cancer screening hasn't led to a significant increase in the prognosis of these tumors. There are not currently any standard treatments for aggressive neuroendocrine tumors of the colon and rectum.⁶ The treatment will, however, depend on the stage of the tumor. If one of these tumors is found in the early stages, a combination of surgery, radiation therapy, and chemotherapy may be considered.

For advanced-stage high-grade neuroendocrine tumors, chemotherapy is the treatment of choice and can result in longer survival. Chemotherapy regimens are similar to those used to treat small cell lung cancer, usually involving platinum drugs such as Platinol (cisplatin) or Paraplatin (carboplatin).