Thyroid adenoma

Thyroid adenoma
Classification and external resources
ICD-9	226
DiseasesDB	13071
MeSH	D013964

A thyroid adenoma is a benign tumor of the thyroid gland.

Types

Almost all thyroid adenomas are follicular adenomas.^[1] Follicular adenomas can be described as "cold", "warm" or "hot" depending on their level of function.^[2] Histopathologically, follicular adenomas can be classified according to their cellular architecture and relative amounts of cellularity and colloid into the following types:

• Fetal (microfollicular) - these have the potential for microinvasion.^[3] These consist of small, closely packed follicles lined with epithelium.^[4]
• colloid (macrofollicular) - these do not have any potential for microinvasion^[3]
• embryonal (atypical) - have the potential for microinvasion.^[3]
• Hürthle (oxyphil) - have the potential for microinvasion.^[3]

Papillary adenomas are very rare.^[3]

Differential diagnosis

A thyroid adenoma is distinguished from a multinodular goiter of the thyroid in that an adenoma is typically solitary, and is a neoplasm resulting from a genetic mutation (or other genetic abnormality) in a single precursor cell.^[5] In contrast, a multinodular goiter is usually thought to result from a hyperplastic response of the entire thyroid gland to a stimulus, such as iodine deficiency.

Careful pathological examination may be necessary to distinguish a thyroid adenoma from a minimally invasive follicular thyroid carcinoma.^[5]

Presentation

A thyroid adenoma may be clinically silent ("cold" or "warm" adenoma), or it may be a functional tumor, producing excessive thyroid hormone ("hot" adenoma). In this case, it may result in symptomatic hyperthyroidism, and may be referred to as a toxic thyroid adenoma.

Morphology

Thyroid follicular adenoma ranges in diameter from 3 cm on an average, but sometimes is larger (up to 10 cm) or smaller. The typical thyroid adenoma is solitary, spherical and encapsulated lesion that is well demarcated from the surrounding Thyroid parenchyma. The color ranges from gray-white to red-brown, depending upon

1. the cellularity of the adenoma
2. the colloid content.

Areas of hemorrhage, fibrosis, calcification, and cystic change, similar to what is found in multinodular goiters, are common in thyroid (follicular) adenoma, particularly in larger lesions.

Management

Most patients with thyroid adenoma can be managed by watchful waiting (without surgical excision) with regular monitoring.^[6] However, some patients still choose surgery after being fully informed of the risks.^[6] Regular monitoring mainly consists of watching for changes in nodule size and symptoms, and repeat ultrasonography or needle aspiration biopsy if the nodule grows.^[6]

References

1. ^ Cotran, Ramzi S.; Kumar, Vinay; Fausto, Nelson; Nelso Fausto; Robbins, Stanley L.; Abbas, Abul K. (2005). Robbins and Cotran pathologic basis of disease. St. Louis, Mo: Elsevier Saunders. pp. 1117. ISBN 0-7216-0187-1. 
2. ^ "Endocrine Pathology". http://library.med.utah.edu/WebPath/ENDOHTML/ENDO037.html. Retrieved 2009-05-08. 
3. ^ ^{a b c d e} emedicine > Thyroid, Evaluation of Solitary Thyroid Nodule > Benign Thyroid Nodules By Daniel J Kelley and Arlen D Meyers. Updated: Oct 17, 2008
4. ^ TheFreeDictionary > microfollicular adenoma Citing: Dorland's Medical Dictionary for Health Consumers. Copyright 2007
5. ^ ^{a b} Ramzi Cotran, Vinay Kumar, Tucker Collins (1999). Robbins Pathologic Basis of Disease, 6th Edition. W.B. Saunders. ISBN 072167335X. 
6. ^ ^{a b c} Treatment section in: Welker, M.; Orlov, D. (2003). "Thyroid nodules". American family physician 67 (3): 559–566. PMID 12588078.  edit [1]

See also

• Thyroid nodule