Is a carcinoid tumor cancer

Carcinoid: benign, malignant?

Carcinoids - What Are They? Benign or Malignant Tumors?

Neither the term neuroendocrine tumor nor the term carcinoid determine whether the patient has a benign or a malignant tumor. In the case of well-differentiated (Ki-67≤2%) neuroendocrine tumors, even nowadays the pathologist cannot always say with certainty whether the tumor is benign or malignant when examining the tumor under the microscope. Often it is only the clinical course that, after months or years, makes it possible to decide with certainty whether the carcinoid is benign or malignant. Reliable evidence for the malignancy of carcinoid tumors is the occurrence of daughter tumors. The penetration of the tumor into the deep wall layers, the involvement of the vessels (angioinvasion) and the histological loss of good differentiation also speak for malignancy.

Degree of differentiation of neuroendocrine tumors

The determination of the degree of differentiation of carcinoids and islet cell tumors in the tissue is decisive for statements about the prognosis but also for the treatment. The pathologist determines the degree of differentiation based on, among other things, immunohistological staining of the tumor. In particular, the rate of cell division and the percentage of tumor cells that stain positive for the proliferation marker Ki-67 are used as “markers”. Well-differentiated tumors are known as G1 neuroendocrine tumors that have a tissue proliferation rate <2% or a Ki-67 rate of ≤2%. Patients with G1-differentiated neuroendocrine tumors generally have a very good prognosis. Tumors with a proliferation rate between 2 and 20% are referred to as G2 tumors; Even G2-differentiated neuroendocrine tumors are nowadays generally considered to be well-differentiated. The vast majority of tumors with a proliferation rate of over 20% are poorly differentiated or even undifferentiated neuroendocrine tumors, which are generally associated with a less favorable prognosis. G3-differentiated, neuroendocrine tumors are referred to as neuroendocrine carcinomas according to the latest WHO classification (from 2010).

Expert advice

Center for Neuroendocrine Tumors
Prof. Hans Scherübl
Vivantes Clinic Am Urban
Academic teaching hospital of the Charité, Berlin
Dieffenbachstrasse 1
10967 Berlin

Tel: (030) 130 225201
Fax: (030) 130 225205