Manisha Bahl MD, MPH, Presenter: Nothing to Disclose

Julie A. Sosa MD, Abstract Co-Author: Nothing to Disclose

Kingshuk Choudhury PhD, Abstract Co-Author: Nothing to Disclose

Nathan Wnuk MSc, BSc, Abstract Co-Author: Nothing to Disclose

Jenny K. Hoang MBBS, Abstract Co-Author: Research support, General Electric Company

To determine trends in imaging-detected incidental thyroid cancer diagnosis and characteristics of incidental and nonincidental cancers.

We performed a retrospective review of 1721 patients who underwent thyroidectomy or lobectomy from 2003 to 2012. Medical records were reviewed for patient demographics and pathology results. For patients with malignancy, incidental cancer was defined as asymptomatic patients presenting with incidental thyroid nodules (ITN) on imaging or those with incidental cancers on the surgical specimen when surgery was performed for another reason. Cancer characteristics were compared for the incidental and nonincidental groups. We observed the 10 year trend in number of surgeries and incidental malignancy. 

Of 1721 patients who underwent surgery, 578 patients had surgically confirmed thyroid cancer, of which 162 (28%) were incidental cancers. 86 (15%) were cancers detected incidentally by imaging and 76 (13%) were cancers detected incidentally on the pathology specimen. Incidental cancers on imaging represent less than 5% of all thyroid surgeries. The mean size of incidental tumors by imaging and pathology were 17 mm and 9 mm, respectively, compared to 21 mm for nonincidental tumors. Nodal metastases were present in 24/86 (28%) of incidental tumors by imaging and 5/76 (7%) of incidental tumors by pathology, compared to 138/416 (33%) for nonincidental tumors. The metastases were confined to the central compartment for incidental cases in 20 of the imaging detected group and all of the pathology group, compared to 81 in the nonincidental group. Over a ten year period, there was a trend in increasing number of thyroid surgeries, malignancies, and incidental malignancies each year. From 2003 to 2012, there was a 181% increase in surgeries (from 77 to 216). The number of malignancies increased from 20/77 (26%) in 2003 to 95/216 (44%) in 2012. The proportion of cancer detected incidentally by imaging increased from 3/77 (4%) to 18/216 (8%).  

Imaging-detected incidental thyroid cancers are uncommon, but have doubled over the last decade. Compared to nonincidental cancers, incidental cancers are less aggressive tumors with lower rates of metastatic disease.

Workup of ITN on imaging may be increasing the number of cancer diagnoses, but they only represent a small proportion of diagnosed malignancies. Guidelines may help to reduce ITN workup.

Bahl, M, Sosa, J, Choudhury, K, Wnuk, N, Hoang, J, Incidental Thyroid Cancers Detected on Imaging: Retrospective Review of a 10-year Experience.  Radiological Society of North America 2013 Scientific Assembly and Annual Meeting, December 1 - December 6, 2013 ,Chicago IL. http://archive.rsna.org/2013/13044322.html