The Trouble with Follicular Tumors
The Trouble with Follicular Tumors
CASE OF THE MONTH
PRESENTED BY
THE THYROID SURGERY CENTER OF TEXAS, P.A.
1927 Lohmans Crossing Road, Suite 201, Austin, TX 78734
www.thyroidcancer.com
512-608-9595; Fax-512-608-9833
The Trouble with Follicular Tumors
Probably the most common masses encountered by the thyroid surgeon are adenomatous tumors and follicular adenomas. These far outnumber the various kinds of thyroid cancer we see, but we often take these tumors out because we can’t be certain of their histology. There is no test, short of removing the tumor, that will give us an accurate diagnosis of the thyroid mass in question. Because the primary pathologic criterion for calling a follicular lesion a carcinoma is capsular invasion, and since an FNA does not get a sample of the capsule, follicular adenomas are virtually impossible to distinguish from follicular carcinoma, thus exposing one of the limitations of that test. Invasion of blood vessels, or angioinvasion, is another diagnostic criterion that is used.
On the following page is a photo of a classic 2cm benign follicular adenoma within the right thyroid lobe. As you can see, its capsule is extremely thin. Also, note the red to pinkish areas that appear “meaty”. These are the “solid” areas seen when an ultrasound is done. At the same time, note the “watery” or mucoid appearing areas. These are probably the result of cystic degeneration of a solid follicular adenoma, and they explain the reason a lot of the ultrasounds you order come back saying “heterogenous” or “partially cystic” lesion. There are very few true cysts of the thyroid.
The presence or absence of capsular invasion and angioinvasion explains why frozen section evaluation of follicular lesions in the operating room has so many limitations. We must always await the final pathology report before reassuring the patient that her tumor was benign. This is why we sometimes have to return the patient to the operating room at a later date for completion of her thyroidectomy if the diagnosis on the final report, that comes a day or two later, proves to be carcinoma, for if the other ‘normal’ side is left in, completion of treatment with radioactive iodine would be severely compromised, if not futile.
Follicular tumors of the thyroid...sometimes a conundrum.
“…Thyroid surgery…it’s all we do…”