The diagnostic value of fused positron emission tomography/computed tomography in the localization of adrenocorticotropin-secreting pituitary adenoma in Cushing's disease.

Despite the high resolution of magnetic resonance imaging (MRI) of the pituitary gland, up to 40% of cases of Cushing's disease (CD) have normal MRI. Fused images of positron emission tomography and computed tomography (PET-CT) may have a potential diagnostic role in CD in general and in such cases in particular. Objective of this study is to explore the diagnostic potential of PET-CT for localization of adrenocorticotropin-secreting pituitary adenomas in CD. PET-CT was performed in 12 cases with de novo (7 cases) or persistent CD (5 cases) that were proven to have CD on biochemical, radiological and/or histopathological findings. These cases had a definite CD confirmed on histopathological and immunostaining examination of the subsequent transphenoidal surgical specimens (10 cases) and/or bilateral inferior petrosal sinus sampling (IPSS, 4 cases). PET-CT was positive in 7 of the 12 cases of CD (58%) showing a focal area of uptake in the pituitary gland. In these seven cases, MRI was positive in six (85.7%) but negative in one case (14.3%). In the other five cases with negative PET-CT, MRI was positive in two and negative in three cases. Of four cases with negative MRI, PET-CT was positive in one case (25%). We conclude that PET-CT is positive in around 60% of the cases of CD. Although the majority of cases with positive PET-CT had positive MRI, PET-CT may detect some cases with negative MRI and thus provides important diagnostic information. If these findings are confirmed in larger studies, PET-CT might become an important diagnostic technique, especially when the more invasive and technically demanding procedure of IPSS is not available or inconclusive.

Obstructive endotracheal lesions of thyroid cancer.

Airway invasion is a life-threatening complication of thyroid cancer. An important issue that deserves better attention is the differentiation between the clinical features of tracheal wall invasion versus those of an obstructive endotracheal lesion. We present information on the clinical course, diagnostic modalities utilized, management instituted, along with the prognosis, and follow-up data on a group of patients presenting with obstructive endotracheal lesions of thyroid cancer. Two thousand four hundred and eighty-nine thyroid cancer patients were seen at our institution from December 1975 to May 2000. Thirteen patients presented with symptoms of respiratory distress related to obstructive endotracheal lesions. At presentation, 11 patients underwent endoscopic examination. Imaging studies consisting of I123 whole body scan (WBS), computed tomography/magnetic resonance imaging (CT/MRI) of neck and chest, whole body positron emission tomography using 18-fluoro-2-deoxy-D-glucose ((FDG)PET) were done, as also was determination of the tumour markers, serum thyroglobulin (TG) and calcitonin. Patients were followed for one to 108 months after the initial presentation. Intraluminal tracheal obstruction was severe in eight patients; five had near-total-occlusion. Paralysis of the vocal folds was present in five. Evidence of metastatic disease was present in most patients. Dissociation between iodine uptake and TG synthesis was evident in five patients during follow-up. Four patients died of cancer. Of the nine living patients; cancer persisted in six, recurred in two patients, and remitted in one. This study has identified obstructive endotracheal lesion of thyroid cancer as a distinct entity apart from tracheal wall disease. These data provide evidence that intraluminal tracheal invasion of thyroid cancer is an ominous sign and a frequent cause of morbidity.