A neoplasm is an abnormal growth of cells, also known as a tumor. Neoplastic diseases are conditions that cause tumor growth -both benign and malignant. Benign tumors are noncancerous growths. They usually grow slowly and can’t spread to other tissues. Malignant tumors are cancerous and can grow slowly or quickly. Malignant tumors carry the risk of metastasis, or spreading to multiple tissues and organs.