October 17, 2023


In pathology, the term undifferentiated is used to describe a malignant (cancerous) tumour made up of cells that look nothing like normal, healthy cells. The degree of differentiation is important because it is used to determine the tumour grade and all undifferentiated tumours are considered high grade. In contrast, well differentiated tumours are considered low grade. Compared to low grade tumours, high grade tumours tend to be more aggressive, are more likely to metastasize (spread) to lymph nodes and other parts of the body, and are associated with worse prognosis. Because the tumour cells look so abnormal when examined under the microscope, additional tests such as immunohistochemistry (IHC) may be performed to determine the original or starting place of the tumour.

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