Current Role of ¹¹¹In-DTPA-Octreotide Scintigraphy in Diagnosis of Thymic Masses

<jats:sec><jats:title>Aims and background</jats:title><jats:p> Thymic tumors (thymomas and thymic carcinomas) represent 50% of all mediastinal tumors. Thymomas usually express high levels of somatostatin receptors, which enable in vivo imaging with <jats:sup>111</jats:sup>In-DTPA-octreotide (OctreoScan®). The aim of this study was to further investigate the role of radionuclide techniques in the diagnosis, staging and follow-up of these tumors. </jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p> Eight patients (5 women, 3 men, age range 35–79 years; mean ± SD 56.1 ± 15.8 years) entered the study. In 4 patients, myasthenia gravis was the presenting symptom. <jats:sup>111</jats:sup>In-DTPA-octreotide scan was performed within 3 weeks after contrast enhanced CT and/or MRI. Planar and tomographic images were acquired within 24 hours of the injection of 111 MBq OctreoScan. The scintigraphic results were defined in correlation with the histological findings. </jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p> Histology revealed thymoma in 3 patients, thymic carcinoma in 1, insular carcinoma of presumably thymic origin in 1, thymic carcinoid in 1, and thymic hyperplasia in 2 patients. Two thymomas were at stage I, 1 thymoma and 1 thymic carcinoma at stage II, 1 insular carcinoma of presumably thymic origin at stage IV, and 1 thymic carcinoid at stage IV. OctreoScan consistently accumulated in primary and/or metastatic sites of thymic tumors while no radiotracer uptake was detected in the 2 patients with benign thymic hyperplasia. In 1 patient with a very large mediastinal mass (13 cm in largest diameter) and multiple metastatic deposits in the lungs, OctreoScan scintigraphy showed a large area of pathological uptake in the anterior mediastinum and a small area of focal uptake in the cervical-dorsal region of the right lung corresponding to a lymph node expressing somatostatin receptors. </jats:p></jats:sec><jats:sec><jats:title>Conclusions</jats:title><jats:p> OctreoScan is avidly taken up by thymic tumors, enabling the diagnosis of these tumors and a better evaluation of their extension. It does not accumulate in thymic hyperplasia, thus allowing the differential diagnosis between these 2 pathological conditions. In patients affected by myasthenia gravis, OctreoScan scintigraphy can play an important role in characterizing thymic masses. </jats:p></jats:sec>