Neoplasia is an abnormal and purposeless augmentation of cells in a tissue or organ. The structure that results from cellular augmentation is called a neoplasm.

The word “neoplasm” is not always synonymous with “cancer”.

Cancer identifies malignant cell growth, whereas neoplasms can be benign or malignant. Additionally, there are tumors that are non-neoplastic.

Examples of Non-Tumorous Neoplasms

• Leukemia
• Cervical Intraepithelial Neoplasia
• Melanocytic Nevi (Moles): These neoplasms are neither tumorous nor cancerous. They are also the most common neoplasms that affect humans.

Definition, or Lack Thereof

Curiously, the biomedical community has not reached a consensus as to what the precise definition of a neoplasm is. The following statement by the British oncologist R.A. Willis is commonly cited – despite its incomprehensiveness, it does offer clear insight into the processes and affects of many neoplasms:

“A neoplasm is an abnormal mass of tissue, the growth of which exceeds and is uncoordinated with that of the normal tissues, and persists in the same excessive manner after cessation of the stimulus which evoked the change.”

The word “tumor” is considered a synonym of “neoplasm”. This synonymy is not precise, but it is accepted in the medical community.

Features

When neoplasia results in a distinct mass of tissue, there are usually multiple cell-types involved, but the initiation and continued growth of the tissue is typically contingent on a single population of neoplastic cells. These are abnormal cells that multiply more than they should and/or do not die when they should.

Clonality

To identify certain forms of cell proliferation as neoplastic, it is necessary to demonstrate that the cell population is genetically identical to a single progenitor cell (clonality). Clonality can be determined if cells grown in vitro propagate indefinitely. Demonstrating clonality is frequently impossible, making it an irregular requisite for the identification of neoplasia.