Thyroid lumps affect roughly 4% to 7% of the Singaporean population; whereby women are four times more likely than men to be affected by it. Most lumps are benign and do not disrupt patients’ everyday life – although some lumps can grow to cause compression symptoms and eventually turn cancerous. A fine-needle aspiration cytology (FNAC) is used to further investigate the cancer progression.

Local study disputes previous data

A recent study, conducted by National University of Singapore (NUH), involved 309 patients who sought treatment at NUH between 2008 and 2014. Researchers found that there is an increased risk of cancer in thyroid nodules classified as “indeterminate” under an international standard. “Indeterminate” essentially means the nodules are regarded as neither particularly worrisome nor safe.

For this study, FNAC was performed on the modules and a pathologist classified them into six categories using an internationally approved standard, the Bethesda System for Reporting Thyroid Cytopathology. Category three, or the “in between” group as doctors call it, is the one that poses some difficulty.

At NUH, roughly 1,000 to 1,500 fine-needle aspirations are conducted on thyroid nodules at every year. Out of these, 6% fall into this “indeterminate” category.

It was previously thought that these nodules would end up being malignant 5% to 15% of the time. This study has found that the risk is much higher as more than 25% of patients will likely develop cancer. This finding corroborates with other global studies that were recently carried out on this topic.

Impact on current management

Assistant Professor Ngiam Kee Yuan, a consultant at NUH's division of general surgery (thyroid & endocrine surgery) and one of the study's authors expressed that “the challenge is how do you offer the right treatment for the patient. Surgery or a follow-up?”

At the moment, guidelines recommend that the patient undergoes a follow-up fine-needle aspiration after an appropriate interval, which is usually three months later. However, with this recently published local study showing that the cancer risk is significantly higher, Prof Ngiam supposed that surgery to remove one half of the thyroid gland might occasionally be a better choice.

A senior consultant at NUH's department of pathology, Associate Professor Nga Min En was also involved in the study. She said that the team also attempted to investigate whether the “difficult category” could be refined further.

“We wanted to see if we could further refine it into patients who are more likely to require surgery versus those who might actually benefit from a repeat fine-needle aspiration,” said Prof Nga.

Researchers discovered that the risk of cancer differed for two types of thyroid nodules – those with architectural atypia in which the cell patterns; are abnormal and nuclear atypia, where the cells have an abnormal nucleus. For thyroid nodules with nuclear atypia, the risk of cancer was found to be 36.8% – as compared to the 14.7% risk for nodules with architectural atypia.

This further concludes that patients who have thyroid nodules that are classified in category three – but with nuclear atypia – might find surgery to be more beneficial, elaborated Prof Nga.

Prof Ngiam hopes that this study will lead to better prospects for patients. “From a clinician-patient perspective, you want to be able to tell patients something you know is validated in Singapore and not in America or Europe,” he said.

This research is the first of its kind to be published and one of the largest of its nature internationally, in terms of sample size. It was published in February 2017 in the Cancer Cytopathology, a peer-reviewed journal of the American Cancer Society (ACS). MIMS

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