[Diagnostic accuracy of 18F-FDG PET in residual or recurrent differentiated thyroid carcinoma with high thyroglobulin and negative 131-I whole-body scan]. / Eficacia diagnóstica de la PET 18F-FDG en el cáncer diferenciado de tiroides residual o recurrente con tiroglobulina elevada y rastreo con 131-I negativo.

INTRODUCTION: 18F-FDG PET has demonstrated its usefulness in detecting recurrences of differentiated thyroid cancer (DTC) with high thyroglobulin (Tg) levels and negative 131I whole-body scan (WBS); however, the number of patients analyzed is low and different studies report disparate results. OBJECTIVE: To estimate the diagnostic accuracy of 18F-FDG PET in this subgroup of patients. MATERIALS AND METHODS: Fifty eight patients (64 18F-FDG PET studies) with histologically proven DTC treated with total thyroidectomy followed by at least one session of 131I therapy for the ablation of thyroid remnants were retrospectively analyzed. Results were verified by pathology, clinical follow-up, response to treatment, or by comparison with conventional diagnostic methods. Sensitivity (Se), specificity (Sp), likelihood ratios (LR), diagnostic accuracy (DA), positive and negative predictive values (PPV, NPV), and Tg levels were calculated for patients with positive and negative 18F-FDG PET results. RESULTS: Twenty seven studies were true positives, 1 false positive, 25 true negatives, and 11 false negatives. Se was 71 %, Sp 96 %, PPV 96.4 %; NPV 69.4 %, DA 81.3 %, positive LR 17.75, and negative LR 0.3. The mean Tg level was 202.34 ng/ml in patients with positive 18F-FDG PET and 40.94 ng/ml in those with negative 18F-FDG PET; the difference between the two groups (161.4 ng/ml) was significant at p <0.05. CONCLUSIONS: 18F-FDG PET is a useful for detecting residual or recurrent DTC in patients with elevated Tg and negative 131I WBS.

[Incidental diagnosis of medullary thyroid carcinoma (MTC) after performing 123I-metaiodobenzylguanidine (123I-MIBG) gammagraphy]. / Diagnóstico de carcinoma medular de tiroides (CMT) de forma casual tras realización de gammagrafía 123I-metayodobencilguanidina (123I-MIBG).

UNLABELLED: The objective of this clinical note is to emphasize diagnostic efficiency of 123I-MIBG scintigraphy in the initial diagnosis and follow-up of medullary thyroid carcinoma within MEN2. MATERIALS AND METHODS: We present the case of a patient who, during a scintigraphic study with 123I-MIBG for the diagnosis of pheochromocytoma, was unexpectedly found to suffer from medullary carcinoma of the thyroid. Prior to performing the test, we proceeded to block uptake into the thyroid gland through the administration of Lugol. We carried out the scintigraphic study by intravenously injecting 370 MBq 123I-MIBG. RESULTS: A pathological uptake of the radiopharmaceutical compound over the right suprarenal gland, and unexpectedly, over the thyroid gland was detected, thus confirming the existence of medullary carcinoma of the thyroid in this patient, and obtaining the diagnosis of Type MEN2A polyglandular syndrome. CONCLUSIONS: From our experience, we can manifest the value of scintigraphy using 123I-MIBG in the diagnosis and localization of medullary carcinoma of the thyroid. Furthermore, it is indicated in patients suspected of MEN, since it makes it possible to reach a diagnosis of this kind of syndrome through the performance of just one test.

[Cushing's syndrome secondary to bronchial carcinoid tumor: contribution of gammagraphy with 111In-DTPA octreotide in the localization diagnosis]. / Síndrome de Cushing secundario a tumor carcinoide bronquial: valor de la gammagrafía con 111In-DTPA octreotide en el diagnóstico de localización.

Bronchial carcinoid (BC) is a rare etiology of Cushing syndrome, and difficulties in differential diagnosis with Cushing's disease are often present. We report two cases in which octreotide scintigraphy was an important diagnostic tool. The first patient showed a 1 cm non-specific pulmonary nodule on CT scan that was positive on scintigraphy, being confirmed by surgery. The second case was a man that had been operated but not cured of an ACTH secreting BC that continued with high ACTH levels and negative localization imaging studies. A subsequent scintigraphy showed a positive image suggestive of recurrence. Octreotide scintigraphy may be considered in patients with suspicion of ectopic ACTH syndrome although a positive image in CT scan be present.