Question

Which of the following is characteristic of a malignant rather than a benign tumour?

• A. Undergoes metastasis
• B. Develop a new blood vessels
• C. Cells divide an unlimited number of times
• D. Grows without needing a growth signal

Answer 1

Answer: (A), (B)

The correct options are
A Undergoes metastasis
B Develop a new blood vessels

Tumours which remain at a single site can usually be dealt with clinically and are therefore regarded as benign. They are usually not life threatening. However, even the cells of benign tumours can grow without receiving a growth signal, and can divide indefinitely. The key point at which a tumour becomes malignant is when cells break free from the initial tumour and spread, via the blood and lymphatic system, to establish themselves in other sites, forming secondary tumours. This is the process of metastasis. Malignant cells multiply quickly. However, to get larger, a tumour has to develop a blood supply to obtain oxygen and nourishment for the new and dividing cells. In fact, a tumour would not grow bigger than the size of a pinhead if it did not also develop a blood supply. Cancer cells make chemicals that stimulate tiny blood vessels to grow around them which branch off from the existing blood vessels. This ability for cancer cells to stimulate blood vessels to grow is called angiogenesis.