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PubMed This is a summary of 4 peer-reviewed journal articles Updated
Endocrinology · Thyroid Cancer

The Diagnostic Journey: From Discovery to Results

At a Glance

Thyroid nodules are often discovered incidentally and evaluated using ultrasound TI-RADS scoring. Suspicious nodules require a fine needle aspiration (FNA) biopsy. Pathologists grade these biopsy cells using the Bethesda System to determine cancer risk and guide treatment decisions.

The path to a thyroid cancer diagnosis often begins unexpectedly. Many thyroid nodules are incidental findings—meaning they are discovered by chance during a CT scan, MRI, or PET scan performed for an entirely different reason, such as after a car accident or during a routine check-up.

It is important to know that benign (non-cancerous) thyroid nodules are incredibly common, found in up to 50% of adults. While it is natural to look for physical signs, symptoms like a visible lump, hoarseness, or difficulty swallowing are not always present. In fact, most thyroid cancers do not cause any noticeable symptoms in their early stages.

If you are waiting 3-4 weeks for a biopsy or a surgical appointment, try not to panic. Because these are typically slow-growing, indolent tumors, this short wait time is entirely safe and will not change your outcome [1].

Step 1: The Ultrasound and TI-RADS

The first major diagnostic tool is a high-resolution ultrasound. Radiologists use a system called ACR TI-RADS to “score” thyroid nodules based on their appearance. They look for specific features that might suggest cancer, such as:

  • Microcalcifications: Tiny “punctate” spots of calcium inside the nodule.
  • Irregular Margins: Edges that are blurry or jagged rather than smooth.
  • Composition: Whether the nodule is solid or filled with fluid (cysts are much more likely to be benign).

The TI-RADS score (TR1 to TR5) helps your doctor decide if the nodule is suspicious enough to require a biopsy or if it can simply be monitored over time.

Step 2: Fine Needle Aspiration (FNA)

If a nodule meets certain size and risk criteria, the next step is a Fine Needle Aspiration (FNA). This is a quick procedure where a very thin needle is used to collect a small sample of cells from the nodule. These cells are then sent to a pathologist for review [2].

Step 3: Understanding the Bethesda System

Pathologists use a standardized framework called the Bethesda System for Reporting Thyroid Cytopathology to describe your FNA results [2]. Each category carries a different Risk of Malignancy (ROM)—the statistical likelihood that the nodule is cancerous [3].

Bethesda Category Name Meaning
I Nondiagnostic Not enough cells were collected; the biopsy may need to be repeated.
II Benign Very low risk of cancer; usually managed with monitoring.
III AUS/FLUS “Atypia of Undetermined Significance.” Some cells look unusual, but not clearly cancerous.
IV Follicular Neoplasm Suspicious for follicular cancer; surgery or molecular testing is often recommended.
V Suspicious for Malignancy High probability of cancer; surgery is typically the next step.
VI Malignant Virtually certain to be cancer.

When Results are Unclear

Categories III and IV are considered “indeterminate.” In these cases, your doctor may recommend molecular testing. These tests look at the DNA and RNA of the cells to identify specific mutations (like BRAF or RAS) that can help predict if the nodule is truly cancerous, potentially saving you from an unnecessary surgery [4]. Importantly, molecular testing is usually performed on the material already collected during your initial FNA, meaning you typically do not need to undergo a second biopsy procedure to get these results. Areas of concern found on PET scans (FDG-avid nodules) also carry a higher risk and almost always require further investigation.

Common questions in this guide

What does a TI-RADS score mean on a thyroid ultrasound?
A TI-RADS score is a rating system radiologists use to assess thyroid nodules based on their ultrasound appearance. A higher score means the nodule has more suspicious features, helping your doctor decide if a biopsy is necessary.
What happens during a fine needle aspiration (FNA) biopsy?
An FNA biopsy is a quick procedure where a very thin needle extracts cells from a thyroid nodule. These cells are then examined under a microscope by a pathologist to determine if the nodule is benign or cancerous.
What does an indeterminate Bethesda result like AUS/FLUS mean?
An indeterminate result means the cells look unusual but are not clearly cancerous or clearly benign. In these cases, your doctor may recommend molecular testing to check for specific genetic mutations that clarify your cancer risk.
Do I need a second biopsy for molecular testing?
Typically, you do not need another biopsy procedure. Molecular testing can usually be performed on the tissue sample that was already collected during your initial fine needle aspiration.
Is it safe to wait a few weeks for my thyroid biopsy or surgery?
Yes. Most thyroid cancers are slow-growing tumors, so waiting three to four weeks for a diagnostic procedure or surgical appointment is generally safe and does not negatively impact your outcome.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.What was my nodule's TI-RADS score, and which specific features led to that score?
  2. 2.My FNA result is Bethesda Category [insert category]—what is the specific 'risk of malignancy' at this facility for that category?
  3. 3.If my results are indeterminate (Category III or IV), do you recommend molecular testing before deciding on surgery?
  4. 4.Was this nodule found incidentally, and does its location on the scan suggest any risk to my vocal cords or windpipe?
  5. 5.Is there any reason to suspect a benign condition like thyroiditis or a Hürthle-cell lesion instead of cancer?

Questions For You

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References

References (4)
  1. 1

    Cytological and Ultrasound Features of Thyroid Nodules Correlate With Histotypes and Variants of Thyroid Carcinoma.

    Sgrò D, Brancatella A, Greco G, et al.

    The Journal of clinical endocrinology and metabolism 2023; (108(11)):e1186-e1192 doi:10.1210/clinem/dgad313.

    PMID: 37265229
  2. 2

    Revised Bethesda System for Reporting Thyroid Cytology: Lessons learned from an appraisal of 5 years of experience in a central hospital.

    El Hag IA, Johnston J, Alessa E, Al Shammari M

    Cytopathology : official journal of the British Society for Clinical Cytology 2021; (32(4)):482-492 doi:10.1111/cyt.12970.

    PMID: 33772905
  3. 3

    Cytological Features of "Non-Invasive Follicular Tumour with Papillary like Nuclear Features" - A Single Institutional Experience in India.

    Amita K, Rakshitha HB, Sanjay M, Kalappa P

    Journal of cytology 2023; (40(1)):28-34 doi:10.4103/joc.joc_192_21.

    PMID: 37179965
  4. 4

    Next-generation sequencing of targetable gene fusions in radioiodine-refractory thyroid cancer: a multicenter study.

    Yoo J, Kim M, Kim HK, et al.

    Endocrine-related cancer 2025; (32(7)).

    PMID: 40569242

This page explains thyroid nodule diagnostic tests and Bethesda scoring for educational purposes only. Always consult your endocrinologist or surgeon to interpret your specific pathology report.

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