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Abstract
The introduction of highly sensitive imaging techniques has made it possible to detect
many non-palpable nodules, or "incidentalomas," in the thyroid. Discovery of these
lesions raises concerns about their malignancy, but the optimal strategy for managing
these lesions has not been clearly established.
To review evidence about incidentalomas, including prevalence and risk for malignancy,
and to provide recommendations for their evaluation and treatment.
Literature searches for relevant articles published in the past 15 years in major
English-language medical journals, review of selected articles published before this
period, and reviews of bibliographies in text-books.
Three studies on autopsy findings, 11 studies on ultrasonographic findings, and other
reports on nonpalpable thyroid nodules were included.
Data on the prevalence of nodules on autopsy and in ultrasonographic series, palpation
compared with ultrasonography, the risk for malignancy in nodules found in irradiated
glands, the natural history of thyroid nodules, and the prevalence of occult cancer
were collated and reviewed.
Prevalence of thyroid incidentalomas estimated from autopsy studies ranges from 30%
to 60%. Studies comparing clinical palpation with thyroid imaging show a prevalence
of 13% to 50%. Prospective studies of randomly selected patients have reported a prevalence
of 19% to 67%. The risk for malignancy in asymptomatic nodules found in nonirradiated
glands is 0.45% to 13% (mean +/- SD, 3.9% +/- 4.1%).
High-resolution ultrasonography is sensitive and capable of detecting many small,
nonpalpable thyroid nodules. Most of these lesions are benign. For most patients with
nonpalpable nodules that are incidentally detected by thyroid imaging, simple follow-up
neck palpation is sufficient.