The role of F-18-fluorodeoxyglucose positron emission tomography in the postoperative evaluation of differentiated thyroid cancer.

OBJECTIVES: The objective of the study was to compare F-18-fluorodeoxyglucose position emission tomography (FDG-PET) with diagnostic whole body scanning (DxWBS) and post-ablation radioiodine whole body scanning (TxWBS) and to assess its prognostic value in newly diagnosed differentiated thyroid cancer (DTC) patients, hypothesizing that FDG-PET is more likely to disclose locoregional and distant metastases. PATIENTS AND METHODS: DxWBS and FDG-PET scanning were performed in 26 newly diagnosed DTC patients who underwent thyroidectomy and TxWBS in 24 cases who had radioactive iodine ablation. The results of the FDG-PET scans were correlated with the stage of the disease and the long-term outcome of DTC. RESULTS: Overall, 18 FDG-PET scans (69.2%) were positive showing a total of 40 foci while 8 scans (30.8%) were negative. The corresponding 26 DxWBS were all positive and showed a total of 47 foci. DxWBS and TxWBS showed similar foci in the 24 patients who had ablation therapy. In contrast to the FDG-PET scans that showed uptake of 26 foci (65%) outside the thyroid bed, 45 foci (95.7%) on DxWBS were in the thyroid bed while 2 foci (4.3%) were in cervical lymph nodes and no focus was seen outside the neck area (P=0.000). There was a clear correlation between the FDG-PET results, the stage of the disease and long-term outcome; seven of the eight negative FDG-PET scans were in stage 1, while all patients with disease higher than stage 1 (six patients) had positive scans. Over a median of 30 months (10-48), seven out of eight patients (87.5%) with negative FDG-PET scans were in remission compared with only eight patients (44.4%) with positive FDG-PET (P=0.04). CONCLUSIONS: In the postoperative evaluation of DTC, compared with DxWBS and TxWBS, FDG-PET scans are more likely to reveal uptake outside the thyroid bed and to correlate with the stage of the disease and long-term outcome.

Diagnostic accuracy of high-resolution neck ultrasonography in the follow-up of differentiated thyroid cancer: a prospective study.

OBJECTIVE: To conduct a prospective study of the diagnostic value of features of cervical lymph nodes (large size, central location, abnormal shape, cystic changes, calcifications, and loss of echogenic hilum), assessed by neck ultrasonography (US), in patients scheduled for surgical treatment of persistent or recurrent differentiated thyroid cancer. METHODS: We studied 152 US abnormalities in 42 patients (median age, 38.5 years) who had undergone one or more neck operations, with or without radioiodine therapy, but continued to have persistent or recurrent disease, which was confirmed by fine-needle aspiration. Another surgical procedure was planned for these patients. On the day of operation, patients underwent a detailed US neck examination by an experienced radiologist. US abnormalities were plotted on a standard diagram of the neck and given specific numbers to help track them during surgical intervention and histopathologic examinations. The US features were compared with the final histopathologic diagnosis. RESULTS: Of 152 US abnormalities, 127 involved cervical lymph nodes and 25 involved other types of tissue. In univariate analysis, size, absent echogenic hilum, cystic changes, calcifications, and central location (medial to the sternomastoid muscle) of cervical lymph nodes were significantly associated with the presence of metastatic involvement. In multivariate analysis, only central location (odds ratio, 4.07; 95% confidence interval [CI], 1.64 to 10.10) and size (odds ratio, 5.14; 95% CI, 1.64 to 16.06) remained significant. The receiver operating characteristic curve for the size of lymph nodes showed a large area under the curve of 0.77 (95% CI, 0.68 to 0.85), and a size of 7.5 mm showed the highest sensitivity and specificity. CONCLUSION: Size and central location of cervical lymph nodes assessed by US during follow-up of patients with differentiated thyroid cancer were the most important predictors of presence of metastatic disease.

Repeated remissions of Cushing's disease due to recurrent infarctions of an ACTH-producing pituitary macroadenoma.

Infarction of prolactin-secreting or growth hormone-secreting pituitary adenomas is not unusual. However, Infarction of ACTH-secreting adenomas has rarely been reported. Cyclical course of Cushing's syndrome alternating with adrenal insufficiency due to recurrent infarction of an ACTH-secreting pituitary adenoma has not been reported. We report here a 20-year-old lady who presented with florid signs of Cushing's syndrome but was found to have adrenal insufficiency on biochemical evaluation. Magnetic resonance imaging (MRI) of the pituitary gland showed that she had infarction of an ACTH-secreting macroadenoma. Over the next 6 years, her disease ran a cyclical course characterized by periods of hypercortisolism alternating with adrenal insufficiency due to repeated episodes of infarctions of the ACTH-secreting pituitary macroadenoma with corresponding changes in the pituitary adenoma on serial MRIs. The case alerts clinicians to this possibility when a patient presents with clinical picture of Cushing's syndrome but has adrenal insufficiency on biochemical testing. It also suggests that silent or subclinical infarction of pituitary adenomas is not uncommon and is probably under diagnosed.