Carcinoid Tumors Renamed Neuroendocrine Tumors

2000: A new name for a new Millennium

Decreased use of the term”carcinoid” and increased use of “neuroendocrine” to describe tumors was driven by disease classifications issued by the World Health Organization. 

In 2000, WHO established the use of “neuroendocrine tumor” over “carcinoid tumor” in its disease classification system.  Since then, the terminology has been refined by WHO as we gain a deeper understanding of this uncommon cancer. 



Slow growing

Well-differentiated Tumors
(Grades 1, 2, and 3)

Neuroendocrine Carcinoma

Fast growing

Poorly-differentiated Tumors
(Grade 3)

WHO classifications create an umbrella name of “neuroendocrine neoplasms.” Low grade or slow-growing cases are called “neuroendocrine tumors.” Higher-grade or fast-growing cases are called “neuroendocrine carcinomas.”

Understanding tumor grade and differentiation

The WHO classifications are diagnostic guidelines for physicians based on tumor grade and other classifications. Most people say neuroendocrine cancer instead of neuroendocrine neoplasm in everyday conversation.

The most worrying connotation of the word 'Carcinoid' is the belief that they all have benign clinical and biological behavior. That is dangerous thinking and has the potential to kill people.”

Ronny Allan,
International NET patient advocate and blogger

Understanding the Basics of Neuroendocrine Tumor (NET) Diagnosis.

Learn more about the history of neuroendocrine cancer and how it develops in this NETWise podcast episode

Exceptions when carcinoid tumor is still used

The above classifications apply to neuroendocrine cancers of the digestive system. In other tumor sites, there are instances when the term carcinoid is still used to classify tumors in the lungs or female reproductive tract by grade.

  • Typical carcinoid tumor: slower growing
  • Atypical carcinoid tumor: faster growing

Carcinoid syndrome and carcinoid cancer

Carcinoid syndrome describes a set of symptoms associated with neuroendocrine tumors. Carcinoid syndrome can cause flushing, bloating, diarrhea, wheezing, cramping, and changes in heartbeat. When these symptoms rapidly elevate, it is called a carcinoid  crisis, a potentially life-threatening medical emergency. Carcinoid syndrome can cause damage to the heart, which is called carcinoid heart disease. 

Carcinoid is a word that signifies how these tumors have been misunderstood. I think almost every NET patient has had the experience of being told, ‘Oh, you don't have a real cancer, you have a NET.’”

Mark Lewis, MD, Intermountain Healthcare

Mark Lewis, MD
Oncologist, Intermountain Healthcare
Member, NETRF Board of Directors

Neuroendocrine is the cell of origin

Unlike other cancer types named for an organ, like breast, brain, or colon cancer, neuroendocrine cancer is named for its cells of origin. Neuroendocrine cells can be found throughout the body. This is yet another way the term neuroendocrine cancer is more accurate than carcinoid cancer. 

11 Irvin M Modlin, Micheal D. Shapiro, Mark Kidd. “Siegfried Oberndorfer: Origins and perspectives of carcinoid tumors.” Human Pathology. 35.12 (2004): 1440-1451.