The etiology of throid adenoma is unknown.
The adenoma represents a initial response to TSH but often either become or are to begin with autonomous.
Initially, the amount of thyroid hormone secreted by the adenoma may be insufficient to cause metabolic disturbance.
However, as the adenoma grows larger and if it remains functional, the patient may exhibit signs of hyperthyroidism.
In such cases, do to feedback inhibition of TSH synthesis, the remainder of the thyroid may become atrophic.,
Thyroid adenomas are not uncommon, solitary nodules in the thyroid.
They can occur at any age.
Females out number males by a ratio of 3 or 4 as to 1.
|General Gross Description|
Grossly, the tumor may be 1 to 10 centimeters in size.
It is soft and fleshy and may have cystic areas.
It is almost always encapsulated and solitary.
|General Microscopic Description|
Microscopically several varieties have been described.
These include the trabecular, fetal, colloid and Hürthle cell.
The trabecular adenoma is composed of sheath cords of small cells.
The fetal adenoma is composed of small follicles, devoid of colloid and embedded in a blue staining, loose matrix.
The colloid adenoma resembles normal thyroid and is composed of normal looking acini filled with colloid.
The Hürthle cell adenoma is composed of acini that are lined by large cells with central nuclei and prominent granular, deeply acidophilic cytoplasm.
The capsule of the adenoma is intact and is composed of fibrous tissue and compressed normal thyroid.
For an adenoma to be a true adenoma and not a follicular carcinoma, there must be no invasion of the capsule by the tumor.
Cotran RS, Kumar V, Robbins SL: Robbins Pathologic Basis of Disease. 5th ed. Philadelphia, W.B. Saunders, 1994, pp. 1134
Harrison's Principles of Internal Medicine, 13th Ed: Isselbach et. al. (eds). New York, McGraw-Hill, 1994, pp. 1948
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||Synopsis by: T.V.Rajan, M.D., Ph.D. (T96000M83300)