Thyroid nodules as small as 2mm can be detected by new technologies such as ultrasound, CT and MRI scanning . Many of these small nodules are papillary thyroid cancers.
In the US, cases have tripled in the past 30 years - from 3.6 per 100,000 in 1973 to 11.6 per 100,000 in 2009 - making it one of the fastest growing diagnoses. Yet the death rate from papillary thyroid cancer has remained stable.
This expanding gap between incidence of thyroid cancer and deaths suggests that low risk cancers are being overdiagnosed and overtreated, argue Dr Juan Brito and colleagues at the Mayo Clinic in Minnesota.
This is exposing patients to unnecessary and harmful treatment that is inconsistent with their prognosis, they warn, and they say both the overdiagnosis and overtreatment of this form of cancer need to be fully recognised.
The article is part of a series looking at the risks and harms of overdiagnosis in a range of common conditions. The series, together with the Preventing Overdiagnosis conference in September, are part of the BMJ
's Too Much Medicine campaign to help tackle the threat to health and the waste of money caused by unnecessary care.
The authors say that unnecessary thyroidectomy (the surgical removal of all or part of the thyroid gland) is costly and carries a risk of complications such as low calcium levels and nerve injury. In the US, the number of thyroidectomies for thyroid cancer has risen by 60% over the past 10 years at an estimated cost of $416m (£270m; €316m).
Using radioactive iodine in patients with low risk thyroid cancer has also increased from one in 300 patients to two in five patients between 1973 and 2006, despite recommendations against using it, they add.
They acknowledge that inferring overdiagnosis of thyroid cancer has limitations, but say that uncertainty about the benefits and harms of immediate treatment for low risk papillary thyroid cancer "should spur clinicians to engage patients in shared decision making ... to ensure treatment is consistent with the research evidence and patient goals."
They suggest a term that conveys favorable prognosis for low risk thyroid cancers (microPapillary Lesions of Indolent Course or microPLIC)) and makes it easier to give patients the choice of active surveillance over immediate and often intensive treatment. And they call for research to identify the appropriate care for these patients.