Follicular Adenoma- Thyroid

 Benign tumor of thyroid
Gross: Solitary encapsulated tumor of variable size. Cut section it is solid and fleshy. The adjacent thyroid tissue  will usually be compressed.
Microscopy:  It is a very well encapsulated tumor, enveloped by a thin fibrous capsule.
The tumor is composed of  closely packed  follicles. There are different patterns like
a.Normofollicular ( the follicles will be of normal size)
b.Microfollicular ( the follices will be very  small. Also called fetal type)
c.Macrofollicular ( the follicles are large and colloid filled )
The lining epithelial cells are low cuboidal to columnar and have a regular nuclei.
The surrounding thyroid will show compressed follicles.

Note that there should not be any tumor tissue within the capsule or within the blood vessels in the capsule or outside the capsule (  which differentiates from follicular carcinoma)