Decisions about the possible management outcomes based on an FNA should be made in consultation with your endocrinologist since every patient has unique circumstances.A fine needle aspiration biopsy using ultrasound is a diagnostic test commonly done on a lump in the thyroid that sometimes cannot be felt by touch. The ultrasound scan uses sound waves to create a picture that can be seen on a monitor, which is like a small television screen. The picture helps the doctors pinpoint the area where the biopsy is to be done. The endocrinologists at Houston Thyroid and Endocrine review the pictures and make a report. The biopsy is removal of tissue or fluid samples from a lump to examine under a microscope. A pathologist is another physician who reviews the biopsy samples and gives a report to the endocrinologist. The results of this procedure can provide information that the doctor needs to determine what treatment is indicated. There are four basic results from a thyroid FNA: 1) Benign 2) Malignant 3) Indeterminate 4) Non-diagnostic insufficient sample Each of these results may determine a different course of action which your endocrinologist will review with you. The below diagram shows diagnostic categories for the FNA biopsy. The gold standard for determining malignancy potential of a nodule is thyroid surgical pathology. If all patients with these categories were sent for surgery the approximate likelihood of malignancy is shown.
Low risk lesionsLymphocytic thyroiditis: This is also known as Hashimoto thyroiditis.Granulomatous thyroiditis: Also known as subacute thyroiditis Colloid nodule: Low to moderate cellularity but also has abundant colloid. Risk of malignancy is <1% Non-diagnostic specimen: There is not enough sample to meet cellular adequacy as defined as 6 well visualized cell groups, each group with at least 10 cells, preferably on a single slide. Risk of malignancy is probably low if the needle was within the nodule but no exact risk can be quoted. Indeterminate lesionsGene analysis can now used on these types of nodules and changes the likelihood of the cancer risk. Treatment plan needs to be individualized depending on patient risk factors, ultrasound characteristics, and other factors.Indeterminate-follicular-lesion, favor-benign: Risk of malignancy is 2 to 10 %. Some institutions would classify these as ACUS. Atypical-cells-of-undetermined-significance (ACUS): Minor features or few cells demonstrating something that if were in greater abundance would be suspicious or malignant. Risk of malignancy is 7 to 20% Follicular lesion: This is a very cellular specimen without nuclear or cellular atypia that would be suspicious for follicular neoplasm. Risk of malignancy is around 7-10%. Hurthle cell lesion: A very cellular specimen without nuclear atypia that would be suspicious for Hurthle cell neoplasm. Risk of malignancy is 7%-45%. Some would not differentiate this from probable malignancy / Hurthle cell neoplasm. Probable MalignancyPatients with these highly suspicious nodules are generally recommended to have an operation to complete the evaluation. Follicular neoplasm: Cellular specimen with a predominant microfollicular pattern with minimal to no colloid or an aspirate which demonstrates unusual findings such as a solid or trabecular pattern, nuclear enlargement and/or irregularity (not Hurthle cell change), mitotic figures or necrosis. Risk of malignancy is 20% Hurthle cell neoplasm: Cellular specimen exclusively composed of Hurthle cells with little colloid. Risk of malignancy is 15-45%. If the aspirate has low cellularity but is composed of pure Hurthle cells, can also be an indeterminate follicular lesion. Suspicious for malignancy: Specimen obtained is just short of a malignant call; at this point the pathologist generally feels the nodule should usually come out with frozen section confirmation prior to total thyroidectomy if clinically indicated. Risk of malignancy is 60-75%. Malignancy: Risk of cancer is almost certain. 97-99%
Biopsy ProcedureDuring the biopsy your doctor will will inject a local anesthetic to numb the underlying skin and tissues. This numbing medication can cause a brief burning sensation. Then a very thin needle is inserted through the skin and into the lump. The needle is thinner than needles used for drawing blood; you may feel a pressure-like sensation which is normal. The doctor will remove a small sample of tissue or fluid from the site. More than one biopsy sample may be taken. Some patients worry that passing a needle through a cancer site might cause it to spread. Studies have shown that this procedure will not affect the spread of cancer. During the biopsy, you will be asked to wait 5-10 minutes while the tissue samples are examined to try to ensure there is enough sample for the pathologist to interpret.After the ProcedureYou may have minor pain and bruising in the area where the biopsy was taken. This does not require medicine other than over the counter acetaminophen. If you have any unusual pain or swelling, call your doctor. Your doctor will receive the final test results usually within 15 business days. Very rare complications can include bleeding, skin infections, inserting the needle into the esophagous or wind pipe, and allergic reactions to lidocaine (no epinephrine is used). Expect a call from the office to discuss the results.The report of a thyroid fine needle biopsy will usually indicate one of the following treatment follow up options: A) The nodule is benign (noncancerous). References:
Edmund S. Cibas, Syed Z. Ali. Thyroid. November 2009, 19(11): 1159-1165. doi:10.1089/thy.2009.0274. MDACC cytopathology internal
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