Pathology dictionary

What does undifferentiated mean?


Undifferentiated cells are cancer cells that do not look anything like the normal cells usually found in the area of the body where the tumour started. Because undifferentiated cancer cells are so abnormal looking when examined under the microscope, your pathologist may not be able to determine the specific tumour type or exactly where the tumour started.

Levels of differentiation

Undifferentiated is on one end of a scale that pathologists call differentiation. This scale is used to compare cancer cells to normal cells. In most areas of the body, the scale includes 4 levels of differentiation.

  • Well differentiated – These tumour cells look very similar to normal, healthy cells but they still behave in a manner that makes them a cancer.
  • Moderately differentiated – These tumour cells are abnormal looking but still share some features with normal, healthy cells.
  • Poorly differentiated – These tumours cells look very little like normal, healthy cells. They often behave in a more aggressive manner compared to better differentiated (well and moderately differentiated) cancers.
  • Undifferentiated – As described above, these tumour cells look and behave nothing like normal, healthy cells.

Additional tests for undifferentiated cells

Your pathologist may order additional tests, such as immunohistochemistry or next generation sequencing (NGS) to better understand an undifferentiated cancer and to try to determine where the cancer started.

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