From Wikipedia, the free encyclopedia
Adenocarcinoma is a cancer originating in glandular
tissue. This tissue is also part of a larger tissue category known as epithelial. Epithelial tissue
includes, but is not limited to, skin, glands and a variety of other tissue that
lines the cavities and organs of the body. Epithelium is derived
embryologically from ectoderm, endoderm and mesoderm. To be classified as
adenocarcinoma, the cells do not necessarily need to be part of a gland, as long as they have
secretory properties. This form of carcinoma can occur in some higher mammals,
Well differentiated adenocarcinomas tend to resemble the glandular tissue that
they are derived from, while poorly differentiated may not. By staining the cells from a
biopsy, a pathologist will determine whether the tumor is an adenocarcinoma or
some other type of cancer. Adenocarcinomas can arise in many tissues of the body
due to the ubiquitous nature of glands within the body. While each gland may not
be secreting the same substance, as long as there is an exocrine
function to the cell, it is considered glandular and its malignant form is
therefore named adenocarcinoma. Endocrine gland tumors, such
as a VIPoma, an
insulinoma, a pheochromocytoma, etc,
are typically not referred to as adenocarcinomas, but rather, are often called
tumors. If the glandular tissue is abnormal, but benign, it is said to be an
adenomas typically do not invade other tissue and rarely metastasize. Malignant
adenocarcinomas invade other tissues and often metastasize given enough time to
A diagnosis of adenocarcinoma which is not further described, known as
adenocarcinoma not otherwise specified or adenocarcinoma NOS, is
significant because it indicates a cancerous process is present.
However, it is not very useful for treatment decisions and prognosis, as these
are determined by the tissue from which the tumour cells arose, i.e. the tissue
of origin; an adenocarcinoma of the colon
has a different prognosis and treatment than an adenocarcinoma of the
Adenocarcinoma not otherwise specified is often a preliminary diagnosis and
can frequently be clarified by a pathologist with the use of
Cancer for which a primary site cannot be found is called cancer of unknown
Examples of tissues where adenocarcinomas may arise:
containing two adenomatous polyps
(the brownish oval tumors above the labels, attached to the normal beige
lining by a stalk) and one invasive colorectal carcinoma
crater-like, reddish, irregularly-shaped tumor located above the
of colonic carcinoid stained by hematoxylin and
The vast majority of colorectal cancer is
an adenocarcinoma. This is because the colon has numerous glands within the
tissue. Normal colonic glands tend to be simple and tubular in appearance with a
mixture of mucus
secreting goblet cells and water
absorbing cells. These glands are called glands because they secrete a substance
into the lumen of the colon, this
substance being mucus. The purpose of these glands are twofold. The first is to
absorb water from the feces back into the blood. The second purpose is to
secrete mucus into the colon lumen to lubricate the now dehydrated feces. This
is crucial as a failure to lubricate the feces can result in colonic damage by
the feces as it passes towards the rectum.
When these glands undergo a number of changes at the genetic level, they
proceed in a predictable manner as they move from benign to an invasive,
malignant colon cancer. In their research paper "Lessons from Hereditary
Colorectal Cancer", Vogelstein, et al., suggested that colon cells lose the APC tumor suppressor gene
and become a small polyp. Next, they suggested that k-Ras becomes activated and
the polyp becomes a small, benign, adenoma. The adenoma, lacking the "carcinoma"
attached to the end of it, suggests that it is a benign version of the malignant
adenocarcinoma. The gastroenterologist uses a colonoscopy to find and remove
these adenomas and polyps to prevent them from continuing to acquire genetic
changes that will lead to an invasive adenocarcinoma. Volgelstein et al. went on
to suggest that loss of the DCC gene and of p53 result in a malignant
Grossly, one will see a mass that looks of a different color than the
surrounding tissue. Bleeding from the tumor is often apparent as the tumor tends
to grow blood vessels into it in a haphazard manner via secretion of a number of
factors such as VEGF. Histologically, a glandular
structure, similar to the healthy normal surrounding glands may be seen. If they
look very similar, this is a low grade, well
differentiated tumor. Often these glands will be disorganized and they will be
seen growing back to back. However, if the tumor does not look like a gland
anymore, it is a high grade tumor with poor differentiation. Regardless of the
grade, malignant tumors tend to have a large nucleus with prominent nucleoli.
There will also be a noticeable increase in the incidence of mitoses, or cell divisions.
Currently, the most common type of lung cancer in lifelong non-smokers is the
Adenocarcinomas account for approximately 10% of lung cancers. This cancer
usually is seen peripherally in the lungs, as opposed to small cell lung
cancer and squamous cell lung cancer,
which both tend to be more centrally located.
The adenocarcinoma has an increased incidence in smokers, but is also the most
common type of lung cancer seen in non-smokers. Adenocarcinoma of the lung tends
to stain mucin positive as it is derived from the mucus producing glands of the
lungs. Similar to other adenocarcinoma, if this tumor is well differentiated
(low grade) it will resemble the normal glandular structure. Poorly
differentiated adenocarcinoma will not resemble the normal glands (high grade)
and will be detected by seeing that they stain positive for mucin (which the
The term adenocarcinoma is derived from 'adeno' meaning 'pertaining to a
gland' and 'carcinoma', which describes a
cancer that has developed in the epithelial cells.
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- ^ Diseases of Lung
- ^ Adenocarcinoma of Lung (Mucin Stain)
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