Adenoma (Adenomas)

Tubular adenoma 2 intermed mag[1]

Adenoma is a benign tumor of epithelial origin and which has glandular characteristics. It may arise from any glandular organ in the body and may rarely transform into a malignant adenocarcinoma.

Presentation

The presentation may depend on the site:

  • Pituitary: Microadenoams may will be asymptomatic, but macroadenomas will cause symptoms due to their mass effect on structures around it. There may be headache and if the adenoma is big enough it may compress the optic chiasma causing visual field loss. Other clinical aspects will depend if the adenoma is secreting hormones such as growth hormone, which may lead to a clinical syndrome called acromegaly [7].
  • Colon: Most colonic polyps are be asymptomatic. The most common symptom being rectal bleeding. Constipation or diarrhea may occur.
  • Adrenal: The symptoms are dependent on the hormone that is being secreted, if any at all. In case of pheochromocytoma, then symptoms that are adrenergic should be sought. Other hormones such as aldosterone may present with electrolyte imbalance symptoms. Corticosteroid excess will present with Cushing syndrome.
  • Thyroid: About 10% of people have an isolated thyroid nodule. Most will be asymptomatic and may present with pressure symptoms only if it is large enough. The few that secrete hormones will have symptoms of hyperthyroidism such as weight loss, irritability, heat intolerance and cardiac rhythm abnormalities like atrial fibrillation.
  • Parathyroid: These may secrete parathyroid hormone and cause primary hyperparathyroidism which will present with symptoms of calcium excess. The clinical syndrome will present with the classic bones, stones, abdominal groans and psychic moans [8] [9] [10].

Workup

The workup is dependent on the site of the adenoma and the symptoms that it is causing.

  • In case of adenoma of the brain, magnetic resonance imaging is the recommended modality as the adenoma may be seen and this will allow planning for treatment if warranted. 
  • For the colon if there is a family history of polyps, whole colon colonoscopy is mandatory otherwise, screening as per local guidelines is recommended.
  • Adrenal adenomas most are found incidentally by CT scan and if there are no symptoms suggestive of hormonal secretion, no more laboratory testing is required. 
  • For the thyroid gland, ultrasound is the modality of choice, with indications for biopsy being determined by features noted on the ultrasound. Thyroid function tests will also be required to examine the hormone levels.
  • Parathyroid adenomas that are symptomatic will require investigations that include calcium levels, urinary calcium levels, renal function tests and parathyroid hormone levels.

Treatment

The treatment of an adenoma will depend entirely on the location and other symptoms caused by the tumor. Many are asymptomatic and will never require any treatment or follow-up. The symptomatic ones may require surgical removal.

Prognosis

The prognosis varies from the site, but the grade of dysmorphic cells and dysplasia is prognostic, with high grades being more prone to malignant transformation than lower grades. There are some familial adenoma syndromes such as familial adenomatous polyposis which is known to have a high propensity for malignant transformation.

Etiology

An adenoma occurs due to an abnormal cell proliferation and defective apoptosis. There are believed to be multiple steps in the progression from normal tissue to adenoma, and then ultimately to adenocarcinoma. The processes differs from site to site and involve loss of tumor suppressor genes and activation of oncogenes. Some of these genetic aberrations may be genetically passed down like in familial adenomatous polyposis (FAP), some may be due to external carcinogens.

Epidemiology

The epidemiology of adenomas varies from site of origin. The list is not exhaustive:

  • Pituitary adenomas represent about 12.5% of all brain tumours [2].
  • Population autopsy studies suggest that approximately 30% of people above 40 years of age have colonic adenomas called polyps [3].
  • Most adrenal adenomas are found incidentally and are termed incidentaloma and their prevalence ranges from 0.4 to 8.7% from autopsy and CT scan studies [4].
  • About 10% of people have an isolated thyroid nodules. Some may require excision of biopsy, and other may secrete hormones [5].
  • Parathyroid adenomas may secrete parathyroid hormone and cause primary hyperparathyroidism [6].

Sex distribution
Age distribution

Pathophysiology

The biochemical processes that lead to adenoma formation depend on the location and the underlying cell type. There may be an interplay of genetic and environmental factors with organs exposed to the environment being at higher risk. The tumorgenesis for many of these is just beginning to be elucidated.

Prevention

Since most are caused by cell proliferation, it is difficult to prevent adenomas. The important aspect it to find the ominous ones early and treat them appropriately to prevent malignant transformation. Families with a strong family history of adenomas like colonic polyps will require screening.

Summary

An adenoma is a benign epithelial tumor with glandular origin, glandular characteristics, or both. It may become malignant and can also appear in non-glandular areas. The malignant transformation is rare. It may cause of other complications such as compressive symptoms and autonomous hormone secretion [1]. The adenomas may be at different levels of dysplasia, with the ones with more dysplastic characteristics, having more potential for malignant transformation.

Patient Information

Definition

Adenomas are small swellings that can occur in many locations in the body. Most of them are innocent, but some may cause trouble if they are big enough and compress nearby structures. They have a small potential to become cancers.

Cause

The cause of the growths is unknown, but there is ongoing research into genetics with information growing.

Symptoms

These depend on the site. In the brain there may be headache and problems with eye site. If they are in the colon there may be constipation or diarrhea otherwise most are asymptomatic. Adrenal tumours may secrete hormones that may cause different symptoms such a weight gain and diabetes if corticosteroid are being made, or episodes of palpitations and flushing if adrenaline is being made. Thyroid adenomas may cause a disease called hyperthyroidism which is presents with heat intolerance and weight loss. Parathyroid adenomas may present with symptoms of too much calcium in the body such as aches and stomach pains.

Diagnosis

Diagnosis is dependent on the site, for the brain a CT scan or magnetic resonance imaging may be used. For the colon a colonoscopy. For adrenal adenomas a CT scan and blood tests to check hormone levels may be done. The same for parathyroid adenomas. For thyroid adenomas an ultrasound may be required and a small piece taken for testing.

Treatment

The response of your doctor will depend on the site and the symptoms and the local guidelines. They may requiring occasional screening or removal by surgery if required.

Self-assessment

References

  1. Mitchell RS, Kumar V, Abbas AK, Fausto N. Robbins Basic Pathology. Philadelphia: Saunders. ISBN 1-4160-2973-7. 8th edition.
  2. Gsponer J, De Tribolet N, Déruaz JP, et al. Diagnosis, treatment, and outcome of pituitary tumors and other abnormal intrasellar masses. Retrospective analysis of 353 patients. Medicine (Baltimore) 1999; 78:236.
  3. Nishihara R, Wu K, Lochhead P, et al. Long-term colorectal-cancer incidence and mortality after lower endoscopy. N Engl J Med. Sep 19 2013;369(12):1095-105
  4. Bovio S, Cataldi A, Reimondo G, et al. Prevalence of adrenal incidentaloma in a contemporary computerized tomography series. J Endocrinol Invest. Apr 2006;29(4):298-302
  5. Hegedüs L. Clinical practice. The thyroid nodule. N Engl J Med 2004; 351:1764.
  6. Wermers RA, Khosla S, Atkinson EJ, Achenbach SJ, Oberg AL, Grant CS. Incidence of primary hyperparathyroidism in Rochester, Minnesota, 1993-2001: an update on the changing epidemiology of the disease. J Bone Miner Res. Jan 2006;21(1):171-7
  7. Levy A, Lightman SL. Diagnosis and management of pituitary tumours. BMJ. Apr 23 1994;308(6936):1087-91.
  8. Shah JP, Hynan LS, Rockey DC. Management of small polyps detected by screening CT colonography: patient and physician preferences. Am J Med. Jul 2009;122(7):687.e1-9.
  9. Nieman LK. Approach to the patient with an adrenal incidentaloma. J Clin Endocrinol Metab. Sep 2010;95(9):4106-13
  10. Castro MR, Gharib H. Continuing controversies in the management of thyroid nodules. Ann Intern Med 2005; 142:926.



Media References

  1. Tubular adenoma 2 intermed mag, CC BY-SA 3.0

Languages