What is Tumor?

Neoplasm (from Ancient Greek νεο- neo- "new" and πλάσμα plasma "formation, creation"), is an abnormal growth of tissue, and when also forming a mass is commonly referred to as a tumor or tumour. This abnormal growth (neoplasia) usually but not always forms a mass.

The World Health Organization (WHO) classifies neoplasms into four main groups: benign neoplasms, in situ neoplasms, malignant neoplasms, and neoplasms of uncertain or unknown behavior. Malignant neoplasms are also simply known as cancers.

Prior to the abnormal growth of tissue, as neoplasia, cells often undergo an abnormal pattern of growth, such as metaplasia or dysplasia. However, metaplasia or dysplasia do not always progress to neoplasia.