If you call me and someone has a thyroglobulin of 1000 or 2000, ultrasound is not going to be my first choice, he said. Because when the thyroglobulin is that high, it almost always means distant metastasis, and the vast majority of the time, it’s metastatic bone disease somewhere. There’s something about bone, and the microenvironment in bone, that even small tumors produce remarkable levels of thyroglobulin. If, on the other hand, the thyroglobulin is in the 100 range, it’s probably lung metastasis. The serum thyroglobulin can point you in the right direction.
Explore This IssueDecember 2006
Imaging Thyroid Cancer
Another major paradigm shift has been the use of ultrasound, often in conjunction with other imaging modalities in the diagnosis, presurgical staging and postoperative management of thyroid cancer.
In the thyroid, only half of nodules even above 1 cm in size are palpable, noted Beth Edeiken, MD, of the University of Texas M. D. Anderson Cancer Center in Houston. In the case of nodules below 1 cm in size-which can be quite biologically aggressive tumors also-94% are nonpalpable and cannot be discovered by physical examination.
When you go to the lymph nodes of the neck, 30 to 50 percent of patients have lymph nodes that can’t be detected by physical examination, Dr. Edeiken said. That’s where ultrasound comes into play.
One problem with ultrasound, she noted, is that it cannot image the area behind the thyroid.
So, often we’ll see one or two lymph nodes that are abnormal in the central compartment, and then our surgeons will find four or five that are behind the thyroid, she said.
From personal experience I think it’s the better modality, if it’s done correctly, to look for recurrences in those deep, dark locations that your fingers can’t find and ultrasound can’t find, said Laurie A. Loevner, MD, a radiologist and neck cancer specialist at the University of Pennsylvania. In the setting of rising thyroglobulin, post-thyroidectomy, clinically negative exam in differentiated thyroid cancer, I would recommend that you start with an ultrasound. If ultrasound is negative, I would move on to an MRI or a CT, whatever you’re more comfortable with. Then you may do PET-CT when ultrasound and MRI are both negative.
Another one of the drawbacks of ultrasound, according to Dr. Tuttle, is the inherent and variable level of user dependency.
The trick with the neck ultrasound is who does it, he said. Because if it’s the same guy that’s doing your gall bladder ultrasound and your testicular ultrasound along with your post-op neck ultrasound, there’s a chance that you’re not going to get very great results.