The Relationship Between Tumor Differentiation and Cancer Prognosis

Among all the reports from cancer workups, one of the most important is the pathology report. It often contains phrases such as "moderately differentiated adenocarcinoma," "poorly differentiated squamous cell carcinoma," or "well-differentiated urothelial carcinoma." What do moderately, poorly, and well differentiated mean? And what does a cancer cell's differentiation have to do with prognosis?

Differentiation is an embryological term: the process by which tissue cells develop from immature to mature. Tumor differentiation refers to the degree to which tumor tissue resembles its normal tissue of origin in morphology and function. The degree of resemblance is the tumor's differentiation grade. A related term is tumor atypia, divided into architectural atypia of the tumor and cellular atypia of the tumor.

Generally, pathology reports grade differentiation into four levels: well, moderately, poorly, and undifferentiated. They may also use "well differentiated" or "poorly differentiated": well-differentiated means a high grade, poorly differentiated a low grade. The higher the differentiation, the more the tumor's morphology and function resemble normal tissue, the smaller the atypia, the lower the malignancy, the better the prognosis, and the longer the patient's survival. The lower the differentiation, the greater the deviation from normal tissue, the larger the atypia, the higher the malignancy, and the worse the prognosis; poorly differentiated tumors are generally harder to treat and have shorter survival.

Of course, differentiation is only one of many cancer measures; prognosis also depends on other factors such as TNM stage. The earlier the stage, the greater the chance of surgery and the better the prognosis; the later the stage, the fewer the treatment options and the worse the prognosis. If a cancer is detected early, even an undifferentiated or poorly differentiated one may be cured by surgery. That is why we should undergo regular physical exams and early cancer screening.