An adenoma is a benign tumor of epithelial tissue with glandular origin, glandular characteristics,
or both.
Adenomas can grow from many glandular organs, including the adrenal glands, pituitary gland,
thyroid, prostate, and others.
Some adenomas grow from epithelial tissue in nonglandular areas but express glandular
tissue structure.
Although adenomas are benign, over time they may transform to become malignant, at which
point they are called adenocarcinomas.
Even while benign, they have the potential to cause serious health complications by compressing
other structures and by producing large amounts of hormones in an unregulated, non-feedback-dependent
manner.
Some adenomas are too small to be seen macroscopically but can still cause clinical symptoms.
Histopathology Adenoma is a benign tumor of glandular tissue,
such as the mucosa of stomach, small intestine, and colon, in which tumor cells form glands
or gland like structures.
In hollow organs, the adenoma grows into the lumen - adenomatous polyp or polypoid adenoma.
Depending on the type of the insertion base, adenoma may be pedunculated or sessile.
The adenomatous proliferation is characterized by different degrees of cell dysplasia irregular
cells with hyperchromatic nuclei,stratified nuclei, nucleolus, decreased mucosecretion,
and mitosis.
The architecture may be tubular, villous, or tubulo-villous.
Basement membrane and muscularis mucosae are intact.
Locations Colon
Adenomas of the colon, also called adenomatous polyps, are quite prevalent.
They are found commonly at colonoscopy.
They are removed because of their tendency to become malignant and to lead to colon cancer.
Renal This is a tumor that is most often small and
asymptomatic, and is derived from renal tubules.
It may be a precursor lesion to renal carcinoma.
Adrenal
Adrenal adenomas are common, and are often found on the abdomen, usually not as the focus
of investigation; they are usually incidental findings.
About one in 10,000 is malignant.
Thus, a biopsy is rarely called for, especially if the lesion is homogeneous and smaller than
3 centimeters.
Follow-up images in three to six months can confirm the stability of the growth.
While some adrenal adenomas do not secrete hormones at all, often some secrete cortisol,
causing Cushing's syndrome, aldosterone causing Conn's syndrome, or androgens causing hyperandrogenism.
Thyroid About one in 10 people is found to have solitary
thyroid nodules.
Investigation is required because a small percentage of these is malignant.
Biopsy usually confirms the growth to be an adenoma, but, sometimes, excision at surgery
is required, especially when the cells found at biopsy are of the follicular type.
Pituitary Pituitary adenomas are seen in 10% of neurological
patients.
A lot of them remain undiagnosed.
Treatment is usually surgical, to which patients generally respond well.
The most common subtype, prolactinoma, is seen more often in women, and is frequently
diagnosed during pregnancy as the hormone progesterone increases its growth.
Medical therapy with cabergoline or bromocriptine generally suppresses prolactinomas; progesterone
antagonist therapy has not proven to be successful.
Parathyroid An adenoma of a parathyroid gland may secrete
inappropriately high amounts of parathyroid hormone and thereby cause primary hyperparathyroidism.
Liver See Hepatocellular adenoma.
Hepatic adenomas are a rare benign tumour of the liver, which may present with hepatomegaly
or other symptoms.
Breast Breast adenomas are called fibroadenomas.
They are often very small and difficult to detect.
Often there are no symptoms.
Treatments can include a needle biopsy, and/or removal.
Appendix Adenomas can also appear in the appendix.
The condition is extremely rare.
The most common version is called cystadenoma.
They are usually discovered in the course of examination of the tissue following an
appendectomy.
If the appendix has ruptured and a tumor is present, this presents challenges, especially
if malignant cells have formed and thus spread to the abdomen.
Bronchial Bronchial adenomas are adenomas in the bronchi.
They may cause carcinoid syndrome, a type of paraneoplastic syndrome.
Sebaceous A sebaceous adenoma is a cutaneous condition
characterized by a slow-growing tumour usually presenting as a pink, flesh-coloured, or yellow
papule or nodule.
Salivary Glands Also major and minor salivary gland adenomas
are common; the parotid gland adenomas are more frequent tends to become adenocarcinomas.
Treatment A physician's response to detecting an adenoma
in a patient will vary according to the type and location of the adenoma among other factors.
Different adenomas will grow at different rates, but typically physicians can anticipate
the rates of growth because some types of common adenomas progress similarly in most
patients.
Two common responses are removing the adenoma with surgery and then monitoring the patient
according to established guidelines.
One common example of treatment is the response recommended by specialty professional organizations
upon removing adenomatous polyps from a patient.
In the common case of removing one or two of these polyps from the colon from a patient
with no particular risk factors for cancer, thereafter the best practice is to resume
surveillance colonoscopy after 5–10 years rather than repeating it more frequently than
the standard recommendation.
See also Adenocarcinoma
References
External links Adrenal adenoma description at 00007 at CHORUS
Photos at Atlas of Pathology