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. • Colloid (macrofollicular) - these do
not have any potential for microinvasion Papillary adenomata are very rare.
Differential diagnosis by age. 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. 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. ==Management==