Malignant tumor: A malignant neoplasm is a cancerous

A malignant neoplasm is a cancerous tumor . It develops when abnormal cells grow, multiply and spread to other parts of your body. Tumor A tumor (neoplasm) is a solid mass of tissue that forms when abnormal cells group together. They can form most anywhere in your body, including your bones, skin, tissue, organs and glands. Many tumors are benign, which means they’re not cancer . You may or may not need treatment for them. Cancerous, or malignant , tumors require cancer treatment. This Patient Page describes benign and malignant tumor classifications. When Is a Tumor Cancer ? All tumors are caused by abnormal, often excessive, cell growth. A malignant neoplasm, or cancerous tumor , usually grows rapidly and can spread into other parts of the body, such as the lymphatic system, blood, or bone marrow. This is part of a process known as metastasis ...