Grades of lung NETs

The grade of a lung neuroendocrine tumour (NET) gives doctors an idea of how the tumour might behave. There are 3 grades of lung NETs.

What is the grade of a tumour

Grading is a way of dividing tumour cells into groups based on how the cells look under the microscope. This gives your doctor an idea of how quickly or slowly the tumour might grow and whether it’s likely to spread.

Grade 1

The cells look very like normal cells. They are also called low grade or well differentiated. Differentiation means how developed or mature a cell is. Cancer cells are not as mature as normal cells.

Grade 1 tumours are usually slow growing and less likely to spread.

Typical carcinoid (TC) is a low grade or well differentiated lung NET.

Grade 2

The cells look more abnormal. They behave somewhere between low grade and high grade tumours. This grade is also called moderately differentiated or intermediate grade.

Atypical carcinoid (AC) is an intermediate grade or moderately differentiated.

Grade 3

The cells look very abnormal. They tend to grow quickly and are more likely to spread. Grade 3 is also called poorly differentiated or high grade.

Large cell neuroendocrine cancer (LCNEC) and small cell lung cancer (SCLC) are high grade or poorly differentiated lung NETs.


Knowing the grade helps your doctor decide which treatment you need. Treatment also depends on:

  • the type of cell the NET started in
  • where the NET is
  • other health conditions you may have
Last reviewed: 
29 Mar 2021
Next review due: 
29 Mar 2024
  • Lung and thymic carcinoids: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up
    E Baudin and others
    Annals of Oncology, 2021. Volume 32, Issue 4 

  • Lung neuroendocrine (carcinoid) tumors: Epidemiology, risk factors, classification, histology, diagnosis, and staging 
    Charles F Thomas and others
    Up to Date, Accessed March 2021

  • Pulmonary neuroendocrine (carcinoid) tumors: European Neuroendocrine Tumor Society expert consensus and recommendations for best practice for typical and atypical pulmonary carcinoids
    M E Caplin and others
    Annals of oncology, 2015. Vol 26, Issue 8, Pages 1604-1620

  • Neuroendocrine tumors of the lung: current challenges and advances in the diagnosis and management of well-differentiated disease
    A E Hendifar and others
    Journal of thoracic oncology, 2016. Vol 12, Issue3, Pages 425-436

  • Cancer: Principles and Practice of Oncology (11th edition)
    VT DeVita and others
    Wolters Kluwer, 2019

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