|-plasia and -trophy|
- Atrophy (reduced functionality of an organ, with decrease in the number or volume of cells)
- Hypertrophy (increase in the volume of cells)
- Hypotrophy (decrease in the volume of cells)
Abiotrophy (loss in vitality of organ or tissue)
- Dystrophy (any degenerative disorder resulting from improper or faulty nutrition)
A neoplasm can be benign, potentially malignant, or malignant (cancer).
- Benign tumors include uterine fibroids, osteophytes and melanocytic nevi (skin moles). They are circumscribed and localized and do not transform into cancer.
- Potentially-malignant neoplasms include carcinoma in situ. They are localised, do not invade and destroy but in time, may transform into a cancer.
- Malignant neoplasms are commonly called cancer. They invade and destroy the surrounding tissue, may form metastases and, if untreated or unresponsive to treatment, will prove fatal.
- Secondary neoplasm refers to any of a class of cancerous tumor that is either a metastatic offshoot of a primary tumor, or an apparently unrelated tumor that increases in frequency following certain cancer treatments such as chemotherapy or radiotherapy.
- Rarely there can be a metastatic neoplasm with no known site of the primary cancer and this is classed as a cancer of unknown primary origin
Neoplastic tumors are often heterogeneous and contain more than one type of cell, but their initiation and continued growth is usually dependent on a single population of neoplastic cells. These cells are presumed to be clonal – that is, they are derived from the same cell,
and all carry the same genetic or epigenetic anomaly – evident of clonality. For lymphoid neoplasms, e.g. lymphoma and leukemia, clonality is proven by the amplification of a single rearrangement of their immunoglobulin gene (for B cell lesions) or T cell receptor gene (for T cell lesions). The demonstration of clonality is now considered to be necessary to identify a lymphoid cell proliferation as neoplastic.
It is tempting to define neoplasms as clonal cellular proliferations but the demonstration of clonality is not always possible. Therefore, clonality is not required in the definition of neoplasia.
Neoplasia vs. tumor
Tumor (American English) or tumour (British English), Latin for swelling, one of the cardinal signs of inflammation, originally meant any form of swelling, neoplastic or not. Current English, however, both medical and non-medical, uses tumor as a synonym for a neoplasm (a solid or fluid-filled cystic lesion that may or may not be formed by an abnormal growth of neoplastic cells) that appears enlarged in size. Some neoplasms do not form a tumor; these include leukemia and most forms of carcinoma in situ. Tumor is also not synonymous with cancer. While cancer is by definition malignant, a tumor can be benign, precancerous, or malignant.
The terms mass and nodule are often used synonymously with tumor. Generally speaking, however, the term tumor is used generically, without reference to the physical size of the lesion. More specifically, the term mass is often used when the lesion has a maximal diameter of at least 20 millimeters (mm) in greatest direction, while the term nodule is usually used when the size of the lesion is less than 20 mm in its greatest dimension (25.4 mm = 1 inch).