From Wikipedia, the free encyclopedia
"Neoplastic" redirects here. For Dutch
artistic movement, see
De
Stijl.
Colectomy specimen
containing a
malignant neoplasm, namely an
invasive
colorectal
carcinoma (the crater-like, reddish, irregularly-shaped
tumor).
Neoplasm is an abnormal mass of tissue as a
result of neoplasia. Neoplasia (new
growth in Greek) is the abnormal proliferation of cells. The growth
of this clone of cells exceeds, and is uncoordinated with, that of
the normal tissues around it. It usually causes a lump or
tumor.
Neoplasms may be benign, pre-malignant or malignant.
In modern medicine, the term tumor is synonymous with a
neoplasm that has formed a lump. In the past, the term
tumor was used differently. Some neoplasms do not cause a
lump.
Types
A neoplasm can be benign, potentially malignant (pre-cancer), or malignant (cancer).
[1]
- Benign neoplasms include uterine fibroids and melanocytic nevi (skin moles). They do not
transform into cancer.
- Potentially malignant neoplasms include carcinoma in
situ. They do not invade and destroy but, given enough time,
will transform into a cancer.
- Malignant neoplasms are commonly called cancer. They invade and destroy the surrounding
tissue, may form metastases and eventually kill the
host.
Difficulty of definition
Because neoplasia includes very different diseases, it is
difficult to find a definition that describes them all.
[2] The definition of the
British oncologist R.A.
Willis is widely cited: 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.[3]
This definition is criticized because some neoplasms, such as
nevi, are not progressive.
Clonality
Neoplastic tumors often 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
descended from a single progenitor cell.
Sometimes, the neoplastic cells all carry the same genetic or epigenetic anomaly
which becomes evidence for 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.[4]
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 (Latin for
swelling) originally meant all forms of swelling, neoplastic or not.
In current English however, both common and Medical, tumor
is now considered synonymous with neoplasm. [5
] Note that some neoplasms do not form a tumor.
They include leukemia and
most forms of carcinoma in situ.
See also
References
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