Neuroendocrine carcinoma (NEC)

Neuroendocrine carcinoma (NEC) is a type of cancer composed of cells that exhibit features of both nerve cells and hormone-producing cells, also known as neuroendocrine cells. These cancers are considered high-grade tumours, which means they tend to grow quickly and may spread to other parts of the body. Neuroendocrine carcinomas can start in many different parts of the body, including the lungs, gastrointestinal tract, pancreas, prostate, and head and neck region.

The term “neuroendocrine carcinoma” in your pathology report means that cancerous neuroendocrine cells were seen under the microscope in the tissue sample that was examined.

What are neuroendocrine cells?

Neuroendocrine cells are specialized cells found throughout the body. They release hormones in response to signals from the nervous system. In normal tissues, neuroendocrine cells help regulate important body functions like digestion, breathing, and blood pressure. When these cells become cancerous, they form tumours that can behave aggressively and may spread to lymph nodes or other organs.

What are the types of neuroendocrine carcinoma?

There are two main types of neuroendocrine carcinoma based on how the tumour cells look under the microscope:

• Small cell neuroendocrine carcinoma – The cancer cells are small with dark round nuclei and little visible cytoplasm. This type is most commonly found in the lungs, but it can also occur in other organs.

• Large cell neuroendocrine carcinoma – The cancer cells are larger and more irregular in shape. This type can also start in the lungs or other organs, such as the gastrointestinal tract or bladder.

Both types are considered poorly differentiated, meaning the cells no longer resemble the normal neuroendocrine cells from which they originated. Poorly differentiated tumours usually grow faster than well-differentiated neuroendocrine tumours and often require more aggressive treatment.

How is this diagnosis made?

The diagnosis of neuroendocrine carcinoma is usually made by examining a biopsy or surgical specimen under a microscope. A pathologist examines the shape, size, and arrangement of the cells, and checks for features such as the number of cells dividing (mitotic activity) and areas of necrosis (dead tumour). These features help confirm that the tumour is high grade.

To support the diagnosis, the pathologist will often perform a test called immunohistochemistry. This test detects specific proteins produced by neuroendocrine cells. Most neuroendocrine carcinomas produce proteins such as synaptophysin, chromogranin A, and CD56. These proteins help confirm that the tumour started from neuroendocrine cells.

What does the grade mean?

Neuroendocrine carcinoma is classified as a high-grade cancer. The term “high grade” refers to cancer cells that are highly abnormal and are growing and dividing rapidly. This is different from well-differentiated neuroendocrine tumours, which are low- or intermediate-grade and usually grow more slowly.

High-grade tumours like neuroendocrine carcinoma are more likely to spread and often require aggressive treatment with chemotherapy, radiation, or both.

What does the stage mean?

The stage of a neuroendocrine carcinoma describes how far the cancer has spread in the body.

Staging usually takes into account:

• The size of the tumour.

• Whether cancer cells have spread to nearby lymph nodes.

• Whether the cancer has spread to other organs (this is called metastasis).

Imaging tests such as CT scans, MRI, or PET scans may be used to determine the stage. A biopsy of nearby lymph nodes or distant sites may also be performed.

Staging helps doctors determine the best treatment and provides an indication of the expected outcome, or prognosis.

What does this mean for treatment?

Treatment for neuroendocrine carcinoma depends on several factors, including the location of the tumour, its stage, and your overall health. Because these tumours grow quickly, treatment usually starts soon after the diagnosis is made. Common treatment options include:

• Chemotherapy – to kill cancer cells throughout the body.

• Radiation therapy – to shrink the tumour or control symptoms.

• Surgery – to remove the tumour if it has not spread.

• Immunotherapy or targeted therapy – may be used in some cases, depending on the tumour’s molecular features.

Your doctor will explain the treatment plan and determine whether additional testing is necessary to inform your decisions.

Questions to ask your doctor

• What type of neuroendocrine carcinoma do I have?

• Where did the cancer start, and has it spread?

• What stage is the cancer?

• What treatment options are available for me?

• Are additional tests needed to guide treatment?

• What is the expected outcome based on my diagnosis?