Understanding Thyroid Nodules
Thyroid nodules are common findings—small lumps or growths that form within the thyroid gland. Most are harmless, but because they can occasionally become cancerous, proper evaluation is essential. Many patients ask: “Can a benign thyroid nodule become malignant?” or “Do benign thyroid nodules grow over time?”
The truth is that while most nodules remain benign, certain biological changes or cellular atypia can signal an increased risk. Knowing how nodules are classified—particularly through systems like the Bethesda category—is key to understanding your results and next steps.
What Is the Bethesda System for Thyroid Nodules?
When a thyroid nodule is biopsied using fine-needle aspiration (FNA), pathologists categorize the cells using the Bethesda classification system. This system helps determine whether the nodule is benign, suspicious, or malignant.
There are six categories in total. Bethesda Category 3, also known as Atypia of Undetermined Significance (AUS) or Follicular Lesion of Undetermined Significance (FLUS), is one of the most challenging to interpret.
A Bethesda Category 3 thyroid nodule means the cells don’t look entirely normal, but they don’t clearly indicate cancer either. It’s essentially a “gray zone” that requires additional testing, close monitoring, or repeat biopsy.
What Does Bethesda Category 3 Mean?
When your biopsy report mentions Bethesda Category III thyroid, or Bethesda 3 thyroid nodule, it means the sample shows mild atypia—changes that might be due to inflammation, benign growth, or early precancerous changes.
Pathologists often use terms like:
- Atypia of Undetermined Significance Bethesda Category III
- Follicular Lesion of Undetermined Significance Bethesda Category 3
This category carries a 5–15% risk of malignancy. Most Bethesda III thyroid nodules turn out to be benign, but since some could represent early thyroid cancer, your endocrinologist may recommend additional evaluation.
Thyroid Nodule Size and Cancer Risk
The size of a thyroid nodule is another important factor in determining its risk. Many patients wonder:
- Is a 2 cm thyroid nodule big?
- What size thyroid nodule is concerning?
- Can a 5 mm thyroid nodule be cancer?
Generally, nodules smaller than 1 cm are rarely malignant, especially if they don’t show suspicious features on ultrasound. However, a 2 cm thyroid nodule or larger often warrants closer evaluation or biopsy.
The thyroid nodule size chart and thyroid nodule size calculator are tools used by specialists to assess dimensions.
For example:
- 1 cm thyroid nodule: Usually monitored unless ultrasound features are suspicious.
- 4 cm thyroid nodule: Typically considered large and evaluated for removal.
- 5 cm thyroid nodule: Significant in size and usually requires diagnostic confirmation.
Nodule size vs width, height, and depth also matters. The thyroid nodule volume calculator or thyroid volume calculator helps estimate total volume to monitor growth trends over time.
Do Benign Thyroid Nodules Grow?
Yes, some benign nodules can grow. Do benign thyroid nodules grow? Absolutely—but growth doesn’t always mean cancer. Hormonal fluctuations, inflammation, or cystic changes can cause nodules to increase in size.
Endocrinologists use serial ultrasounds to track nodule size thyroid cancer risk and detect rapid changes.
If a benign nodule doubles in volume or grows more than 20% in diameter, it’s usually re-evaluated through another biopsy or thyroid ultrasound.
A benign nodule turning malignant (can benign thyroid nodules turn malignant) is uncommon, but not impossible. That’s why consistent follow-up and appropriate testing are so important.
Interpreting Suspicious Nodules on Ultrasound
Ultrasound is crucial for assessing thyroid nodules. Radiologists classify nodules using systems like TI-RADS or TIRADS 4A calculator to rate the level of suspicion.
A suspicious thyroid nodule may show:
- Irregular or spiculated margins
- Microcalcifications
- Taller-than-wide shape
- Increased blood flow
If your provider mentions a TR4 nodule, it means the nodule is moderately suspicious and may need biopsy. The early stage thyroid nodule size chart helps doctors decide when to test or monitor.
How Common Is Thyroid Cancer in Nodules?
Most thyroid nodules are benign, but it’s understandable to worry about malignancy. You may ask:
- What percentage of thyroid nodules are cancerous?
- Roughly 5–10% of all thyroid nodules are malignant.
- What percent of thyroid biopsies are cancerous?
- Among those biopsied, about 10–15% show malignant cells.
This means the majority are harmless. However, the risk increases with certain features, such as family history, radiation exposure, or suspicious ultrasound appearance.
Can a Benign Thyroid Nodule Become Malignant?
A benign thyroid nodule can rarely become malignant, but it’s not common.
Malignant transformation may occur when long-standing benign nodules accumulate mutations over time, especially if they’re large or growing.
Can benign thyroid nodules become cancerous? Yes, though it’s rare. Regular monitoring and periodic imaging are the best ways to detect any change early.
Endocrinologists track growth using tools like the thyroid nodule size chart mm or thyroid nodule calculator to quantify changes objectively. If the nodule grows quickly or develops new features, a repeat biopsy might be recommended.
Additional Symptoms: Hypothyroidism and Hot Flashes
Some patients with thyroid conditions experience hormonal symptoms like hot flashes.
You may wonder:
- Can hypothyroidism cause hot flashes?
- Does hypothyroidism cause hot flashes?
While hot flashes are typically associated with menopause, hypothyroidism hot flashes can occur due to hormonal imbalances affecting body temperature regulation. Treating hypothyroidism often improves these symptoms over time.
When to Seek Medical Attention
You should see your endocrinologist if you notice:
- Rapid growth of a thyroid lump
- Persistent neck pressure or discomfort
- Hoarseness or swallowing difficulties
- Visible asymmetry in the neck
Even if you’ve been told your nodule is benign, it’s important to follow up with periodic imaging.
Some Bethesda Category 3 thyroid nodules remain stable for years, while others may evolve into higher-risk categories, requiring additional testing or intervention.
The Role of Endocrinology Specialists
Endocrinologists play a vital role in managing thyroid nodules and interpreting biopsy results. At Park Avenue Endocrinology & Nutrition, Dr. Shira Eytan, board-certified in Endocrinology, Diabetes, and Metabolism, helps patients understand complex findings like Bethesda III thyroid nodules and provides long-term care to monitor thyroid health.
Her approach combines careful tracking of thyroid nodule size, review of lab results, and advanced imaging to ensure that patients receive accurate, individualized care.
Final Thoughts
A Bethesda Category 3 thyroid nodule doesn’t mean you have cancer—it simply signals uncertainty that needs attention. While benign thyroid nodules rarely turn malignant, ongoing evaluation is the safest way to prevent complications.
Using tools like the thyroid nodule calculator or thyroid volume calculator, and maintaining consistent follow-up with your endocrinologist, ensures that any concerning changes are caught early.
If you’re navigating thyroid biopsy results or wondering about can benign thyroid nodules grow or turn malignant, consulting a thyroid specialist like Dr. Shira Eytan can give you the clarity and confidence you need to move forward.
