ABBREVIATIONS & DEFINITIONS
Thyroid nodule: an abnormal growth of thyroid cells that forms a lump within the thyroid. Thyroid nodules can be benign (non-cancerous) or malignant (cancerous).
Thyroid Ultrasound: a common imaging test used to evaluate the structure of the thyroid gland. Ultrasound uses soundwaves to create a picture of the structure of the thyroid gland and accurately identify and characterize nodules within the thyroid. Ultrasound is also frequently used to guide the needle into a nodule during a thyroid nodule biopsy.
Thyroid fine needle aspiration biopsy: a simple procedure that is done in the doctor’s office to determine if a thyroid nodule is cancerous or not. The doctor uses a very thin needle to withdraw cells from the thyroid nodule. Patients usually return home or to work after the biopsy without any ill effects.
Cytology: a branch of pathology, the medical specialty that examines tissue samples from the body to diagnose different diseases and conditions. Thyroid cytology examines thyroid cells removed during the FNA of thyroid nodules to diagnose thyroid cancer.
Bethesda System for Thyroid Cytopathology: a standardized system to report thyroid FNA specimens, which includes six diagnostic categories: non-diagnostic or unsatisfactory; benign; atypia of undetermined significance or follicular lesion of undetermined significance (AUS/FLUS); follicular neoplasm or suspicious for a follicular neoplasm (FN/SFN); suspicious for malignancy; and malignant.
Indeterminate thyroid biopsy: this happens when a few atypical cells are seen but not enough to be abnormal (atypia of unknown significance (AUS) or follicular lesion of unknown significance (FLUS)) or when the diagnosis is a follicular or Hurthle cell lesion. Follicular and Hurthle cells are normal cells found in the thyroid. Current analysis of thyroid biopsy results cannot differentiate between follicular or Hurthle cell cancer from noncancerous adenomas. This occurs in 15-20% of biopsies and often results in the need for surgery to remove the nodule.
Follicular neoplasm: A tumor that can be benign such as a thyroid adenoma, or malignant such as a follicular thyroid cancer. Fine needle aspiration cannot differentiate between benign and malignant tumors, since all follicular neoplasms show similar results with many thyroid cells arranged in small groups (microfollicular pattern).
Follicular thyroid cancer: the second most common type of thyroid cancer.
Molecular testing: techniques used to examine genes and microRNAs expressed in thyroid cells to differentiate between benign and malignant thyroid nodules. The two most common molecular marker tests are the AfirmaTM Gene Expression Classifier and ThyroseqTM .