What Are The Different Types Of Neuroendocrine Tumors?


Table of Contents

This article will take you through the various types of neuroendocrine tumors.

Let's start off with the basics- What is the endocrine system?

The endocrine system is made up of the hormone-producing cells. It carries the hormones directly into the circulatory system from where it is sent off to the distant target organs.

What is a neuroendocrine tumor (NET)?

Neuroendocrine tumors are neoplasms that are formed from the cells of the endocrine system and the nervous system. These tumors can be formed anywhere inside the body but are most commonly formed in the intestine, where they are referred to as carcinoid tumors. Most of these tumors are benign while some are malignant. Since the cells of these neoplasms have common features, they are treated as a group of tissues.

There are different kinds of neuroendocrine tumors such as:

Gastrointestinal neuroendocrine tumours (GI NETs): These tumors develop in the organs of the gastrointestinal tract. They mainly develop in the gastrointestinal tract as carcinoid and pancreatic islet-cell tumors. Most of these tumors grow very slowly.

Lung neuroendocrine tumours (lung NETs): These tumors are formed in the lungs and the airways. They are most commonly formed in the airways from where they branch off to the lungs through the windpipe.

NETs can be further classified into 4 subtypes:

Typical carcinoid tumours: These are formed in the lungs but since they act like normal cells, they cause little or no pain. They tend to grow slowly.

Atypical carcinoid tumours: Just like typical carcinoid tumors, these tumors act like normal cells and grow slowly. However, these tumors can be well-differentiated and can spread to the other parts of the body.

Small cell lung neuroendocrine carcinomas: These tumors are poorly differentiated. They tend to grow rapidly and often spread to other parts of the body.

Large cell lung neuroendocrine carcinomas: These tumors are aggressive tumors that grow very quickly. They are very poorly differentiated and can possibly spread to other parts of the body.

Pancreatic neuroendocrine tumours (pNETs): These tumors look like the islet cells of the pancreas. These tumors are named based on the type of hormone they produce such as insulinoma, gastrinoma, ACTHome, VIPoma, somatostatinoma, glucagonoma, etc.  

Medullary carcinoma: Medullary carcinoma is named after its appearance as it resembles the tissues of the medulla oblongata. This type of tumor arises from the mid-layer tissues of a particular organ.

Parathyroid cancer: In parathyroid cancer, malignant cancer cells are formed in the parathyroid gland. It is a rare form of cancer. Having inherited disorders can increase the risk of developing parathyroid cancer.

Thymic neuroendocrine cancer: Thymic neuroendocrine cancer includes uncommon thymic neoplasms with neuroendocrine differentiation. It develops distant metastases, in some cases, after long intervals. It is a rare and malignant tumor.

Pheochromocytoma: Pheochromocytoma is a hormone-secreting tumour that forms in the adrenal glands. This results in the secretion of excess epinephrine and norepinephrine. This tumor is malignant in 10% of the cases.

Paraganglioma: This is a very rare neuroendocrine neoplasm which develops at various parts of the body like the neck, head, abdomen, etc. They are categorized by a strong vascularisation and is benign in most of the cases.  

Pituitary gland tumors: The pituitary gland is a small gland that is part of the endocrine system. These tumors are formed in the cells of the pituitary gland and they do not metastasize to the other parts of the body. However, they might grow and expand to the nearby areas.

Merkel cell carcinoma: This is a type of non-melanoma skin cancer that starts in the Merkel cells. They usually start in the areas of the skin that is highly exposed to the sun. It is a rare form of tumor but is quite aggressive and can potentially spread to the other parts of the body.

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