A Patient with Papillary Carcinoma of the Thyroid with Elevated Serum Thyroglobulin but Negative Imaging Studies

Abstract

The patient presented with rather aggressive papillary thyroid cancer, which after initial therapy had evidence of residual disease based upon measurable thyroglobulin levels but which could not be anatomically located. Thus, she illustrated the not infrequent dilemma facing clinicians: the thyroglobulin-positive imaging-negative patient, indicating the presence of occult disease, i.e., a biochemically incomplete response to therapy. In such patients, given that there is no explanation for the loss of radioiodine uptake other than the possibility that tumor deposits are small and below the detection sensitivity of the imaging modality versus dedifferentiation of the tumor, further identification of the source of the thyroglobulin and further treatment become problematic. The utility of other imaging modalities, including FDG-PET/CT, and the merits of empiric radioiodine therapy are discussed.