A well-differentiated tumor is typically described as which of the following?

• A. Malignant and highly invasive
• B. Metastatic with poor prognosis
• C. Benign
• D. Undifferentiated and anaplastic

Answer: (C)

Differentiation describes how closely tumor cells resemble the normal tissue they came from. A well-differentiated tumor retains many features of the original tissue—cell shape, organization, and even some normal functions—which usually means the cells are less abnormal, grow more slowly, and invade surrounding areas less aggressively. Because of this closer resemblance to normal tissue and its more restrained behavior, well-differentiated tumors are typically described as benign. The other descriptors imply more aggressive biology: malignant and highly invasive refers to cancers that invade and destroy nearby tissue, metastatic with poor prognosis indicates spread to distant sites, and undifferentiated and anaplastic denotes loss of normal cell features with high-grade, aggressive behavior.