PHOENIX — The rate of thyroid cancers identified incidentally during nonthyroid imaging procedures is on the rise, Matthew T. Tallar said at a congress sponsored by the Association for Academic Surgery and the Society of University Surgeons.
These incidental thyroid cancers deserve to be taken very seriously because they often present as late-stage malignancies, added Mr. Tallar, a medical student at the Medical College of Wisconsin, Milwaukee.
“Based on our data, we feel that incidental thyroid cancers are indeed clinically significant and that their diagnostic work-up and treatment should be the same as for palpable thyroid nodules,” he said.
The overall incidence of thyroid cancer climbed 2.4-fold in the United States during 1993–2002. The reasons aren't fully known, but the trend has occurred in tandem with the greatly increasing use of diagnostic imaging studies throughout all of medicine.
It is believed that much of the overall rise in thyroid cancer is attributable to a jump in nonpalpable thyroid cancers detected incidentally on cervical imaging studies done for nonthyroid indications, according to Mr. Taller.
His review of all 102 patients operated on for thyroid cancer by endocrine surgeons at the Milwaukee medical center during 2001–2006 showed incidental thyroid cancer in 17%. Moreover, the proportion of thyroid cancers detected incidentally on nonthyroid radiologic studies increased over time. None of 19 cancers operated on in 2001 was detected incidentally, compared with 1 of 17 in 2002, 3 of 17 in 2003, 5 of 15 in 2004, 4 of 20 in 2005, and 4 of 14 in the first half of 2006.
Incidental thyroid cancers were found on MRI, CT, ultrasound, chest x-ray, and carotid duplex ultrasound. The imaging studies were conducted for evaluation of cervical neck pain, carotid arterial disease, voice change, pulmonary metastases, and postnephrectomy follow-up.
Papillary carcinoma was the pathology in 14 of 17 cases; follicular carcinoma was identified in two cases and medullary carcinoma in one.
Overall, 10 patients had stage I cancer. Six had stage III and one had stage IVa disease, for a combined 41% prevalence of late-stage disease.
Audience members expressed interest in a related research question: What proportion of incidentally detected thyroid abnormalities turn out to be cancer?
Mr. Tallar replied that several large studies have recently addressed this very issue.
Radiologists at Lenox Hill Hospital, New York, reviewed all 225 dedicated thyroid sonographic studies they performed in a 6-month period and found that 16% were done to evaluate thyroid nodules earlier discovered incidentally on MRI, CT, or ultrasound performed for nonthyroid indications.
Of biopsied nodules in the incidental group, 17% proved to be cancer, an unexpectedly high rate compared with the 3% for nonincidental nodules—that is, nodules that were palpable or whose presence was signaled by laboratory abnormalities or symptoms of thyroid disease (J. Ultrasound Med. 2005;24:629–34).
And one or more incidental thyroid abnormalities were identified in 165 of 2004 consecutive patients undergoing carotid duplex ultrasound for evaluation of carotid arterial disease in the vascular surgery clinic at Madigan Army Medical Center, Fort Lewis, Wash.
Among those patients with a thyroid abnormality on duplex ultrasound who went on to a dedicated thyroid ultrasound exam, 7.6% were eventually determined to have thyroid cancer (Arch. Surg. 2005;140:981–5).
Although widely used pathways exist for the evaluation and management of large palpable and/or symptomatic thyroid nodules, the best approach to thyroid “incidentalomas” remains controversial.
Mr. Tallar said that the experiences that have been reported from Lenox Hill, Madigan, and Wisconsin indicate that an aggressive approach to the evaluation of thyroid cancer is warranted.