A thyroid adenoma is a

benign tumor A benign tumor is a mass of cells ( tumor) that does not invade neighboring tissue or metastasize (spread throughout the body). Compared to malignant (cancerous) tumors, benign tumors generally have a slower growth rate. Benign tumors have r ...

of the

thyroid gland The thyroid, or thyroid gland, is an endocrine gland in vertebrates. In humans it is in the neck and consists of two connected lobes. The lower two thirds of the lobes are connected by a thin band of tissue called the thyroid isthmus. The thy ...

, that may be inactive or active (functioning autonomously) as a toxic adenoma.

Signs and symptoms

A thyroid adenoma may be clinically silent ("cold" adenoma), or it may be a functional tumor, producing excessive

thyroid hormone File:Thyroid_system.svg, upright=1.5, The thyroid system of the thyroid hormones T3 and T4 rect 376 268 820 433 Thyroid-stimulating hormone rect 411 200 849 266 Thyrotropin-releasing hormone rect 297 168 502 200 Hypothalamus rect 66 216 386 25 ...

("warm" or "hot" adenoma). In this case, it may result in symptomatic

hyperthyroidism Hyperthyroidism is the condition that occurs due to excessive production of thyroid hormones by the thyroid gland. Thyrotoxicosis is the condition that occurs due to excessive thyroid hormone of any cause and therefore includes hyperthyroidis ...

, and may be referred to as a toxic thyroid adenoma.

Diagnosis

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 parenchyma. The color ranges from gray-white to red-brown, depending upon # the cellularity of the adenoma # 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.

Types

Almost all thyroid adenomata are follicular adenomata. Follicular adenomata can be described as "cold", "warm" or "hot" depending on their level of function. Histopathologically, follicular adenomata 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. These consist of small, closely packed follicles lined with epithelium. *Colloid (macrofollicular) - these do ''not'' have any potential for microinvasion *Embryonal (atypical) - have the potential for microinvasion. * Hürthle cell adenoma (oxyphil or oncocytic tumor) - have the potential for microinvasion. *

Hyalinizing trabecular adenoma Hyalinizing trabecular adenoma (or Hyalinizing trabecular adenoma) is a subtype of thyroid adenoma A thyroid adenoma is a benign tumor of the thyroid gland, that may be inactive or active (functioning autonomously) as a toxic adenoma. Signs and s ...

Papillary adenomata are very rare.emedicine > Thyroid, Evaluation of Solitary Thyroid Nodule > Benign Thyroid Nodules
By Daniel J Kelley and Arlen D Meyers. Updated: Oct 17, 2008

Differential diagnosis

A thyroid adenoma is distinguished from a

multinodular goiter A goitre, or goiter, is a swelling in the neck resulting from an enlarged thyroid gland. A goitre can be associated with a thyroid that is not functioning properly. Worldwide, over 90% of goitre cases are caused by iodine deficiency. The term is ...

of the thyroid in that an adenoma is typically solitary, and is a

neoplasm A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...

resulting from a genetic

mutation In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, m ...

(or other genetic abnormality) in a single precursor cell. In contrast, a multinodular goiter is usually thought to result from a

hyperplastic Hyperplasia (from ancient Greek ὑπέρ ''huper'' 'over' + πλάσις ''plasis'' 'formation'), or hypergenesis, is an enlargement of an organ or tissue caused by an increase in the amount of organic tissue that results from cell proliferatio ...

response of the entire thyroid gland to a stimulus, such as

iodine deficiency Iodine deficiency is a lack of the trace element iodine, an essential nutrient in the diet. It may result in metabolic problems such as goiter, sometimes as an endemic goiter as well as congenital iodine deficiency syndrome due to untreated cong ...

. Careful

pathological Pathology is the study of the causes and effects of disease or injury. The word ''pathology'' also refers to the study of disease in general, incorporating a wide range of biology research fields and medical practices. However, when used in th ...

examination may be necessary to distinguish a thyroid adenoma from a minimally invasive

follicular thyroid carcinoma Follicular thyroid cancer accounts for 15% of thyroid cancer and occurs more commonly in women over 50 years of age. Thyroglobulin (Tg) can be used as a tumor marker for well-differentiated follicular thyroid cancer. Thyroid follicular cells are th ...

Management

Most patients with thyroid adenoma can be managed by

watchful waiting Watchful waiting (also watch and wait or WAW) is an approach to a medical problem in which time is allowed to pass before medical intervention or therapy is used. During this time, repeated testing may be performed. Related terms include ''expe ...

(without surgical excision) with regular monitoring. However, some patients still choose surgery after being fully informed of the risks. Regular monitoring mainly consists of watching for changes in nodule size and symptoms, and repeat ultrasonography or needle aspiration biopsy if the nodule grows.Treatment section in:

/ref> For patients with benign thyroid adenomata, thyroid lobectomy and isthmusectomy is a sufficient surgical treatment. This procedure is also adequate for patients with minimally invasive thyroid cancer. When histological examination shows no signs of malignancy, then no further intervention is required. These patients should continue to have their thyroid hormone status regularly checked.

References

External links

{{Endocrine gland neoplasia Thyroid cancer