The rapid increase in the number of thyroid cancers diagnosed over the past decade is being driven by low-risk cases that would never pose a health threat to patients -- and one-third of these are asymptomatic cases being diagnosed with advanced medical imaging.
That's according to a new study in the September issue of Thyroid by researchers from the Mayo Clinic in Rochester, MN. They believe the treatment for these cancers may be causing harms that otherwise might never have occurred (Vol. 25:9, pp. 999-1007).
A team led by Dr. Juan Brito analyzed data from the Rochester Epidemiology Project, gathering the records of 566 men and women who were diagnosed with thyroid cancer in Olmsted County between 1935 and 2012. They specifically focused on the number of new cases of thyroid cancer, deaths from the disease, and the method of diagnosis.
Brito and colleagues found that the number of new cases of thyroid cancer had nearly doubled, from a rate of 7.1 cancers per 100,000 people from 1990 to 1999, to 13.7 cases per 100,000 people from 2000 to 2012. The group also noted the following:
- There was no change in the number of new patients presenting with symptomatic thyroid cancer over the study period.
- The number of new cases of "silent" thyroid cancer -- with no symptoms -- almost quadrupled.
- The proportion of patients who died of thyroid cancer did not change.
Silent thyroid cancer was often identified as an incidental discovery during an imaging test, at 19% of cases. Meanwhile, 27% of cases came from patients with symptoms or palpable nodules that were not clearly associated with thyroid cancer but which triggered the use of imaging tests of the neck. Silent thyroid cancer was also found during the review of thyroid tissue removed for benign conditions, at 14% of cases.
One approach to reduce the detection of lesions that are not a health threat would be to limit the use of some imaging technologies, in addition to engaging patients in considering their treatment options, the authors recommended. Active surveillance could be preferred over surgery in such cases, they added.
Finally, another approach could be as simple as not using the term "cancer" to refer to small, silent thyroid lesions, according to Brito. He recommended a term such as "papillary lesions of indolent course," instead of cancer.
![Examples of ultrasound findings and techniques. (A) Images in a 39-year-old male patient with a mass in the left thigh. The mass is heterogeneous on the B-mode US image (compared with the patient in D) and showed increased microvascularity (superb microvascular imaging [SMI]) and shear-wave elastography (SWE) values. Undifferentiated pleomorphic sarcoma was diagnosed at biopsy (with pleomorphic rhabdomyosarcoma in surgical specimen). (B) Images in an 18-year-old male patient with a mass in the left leg. The mass is hypoechoic on the B-mode image, with no other findings suggestive of malignancy. The lesion is in contact with the cortex of the tibia, which is slightly irregular. CT revealed a doubtful anteromedial tibial erosion. The microvascular study demonstrated high vascularization, suggestive of malignancy. Periosteal Ewing sarcoma was diagnosed with both histologic and immunohistochemical confirmation. (C) Images in a 69-year-old female patient with a lump growing on the outside of the left leg. Multiple SWE examinations were performed (please note the high values obtained in the measurements, whereas the color map highlights the stiffness relative to adjacent tissues). SMI showed areas of increased vascularization to target for sampling. Undifferentiated spindle cell sarcoma was diagnosed at biopsy, with residual leiomyosarcoma in the surgical specimen after neoadjuvant therapy. (D) Images in a 56-year-old female patient with a mass in the right thigh. The mass is heterogeneous at both B-mode ultrasound (similar to patient A) and MRI (coronal T2-weighted spectral attenuated inversion recovery [SPAIR]; T1-weighted pre-contrast and postcontrast imaging), which even shows uptake after the administration of paramagnetic contrast material, which is traditionally suggestive of malignancy. Low values at SMI and elastography are suggestive of benignity. Spindle cell lipoma was diagnosed at biopsy, with atypical spindle cell lipomatous tumor in the surgical specimen.](https://img.auntminnie.com/mindful/smg/workspaces/default/uploads/2026/08/images-radiol250278fig2.APCFLSvX6p.jpg?auto=format%2Ccompress&dpr=2&fit=crop&h=167&q=70&w=250)
