Thymic uptake after high-dose I-131 treatment in patients with differentiated thyroid carcinoma: A brief review of possible causes and management

Abstract

Purpose: To report five cases of patients diagnosed with differentiated thyroid carcinoma (DTC) with uptake in the thymic area after high-dose treatment with I-131 and to evaluate the potential causes and therapeutic management. Methods: Five cases of young female patients with a mean age of 36.6 years (24---43) who had been treated with a mean dose of 106 mCi of I-131 (100---150 mCi) showing tracer uptake in the thymic area are reported. An I-131 whole-body scan (131I-WBS) was performed 7 days after therapeutic dose administration to each patient. Anterior and posterior planar images, followed by SPECT/CT of the head, neck and superior mediastinum were acquired in all patients. Thyroglobulin levels were measured with and without hormone replacement therapy in all cases. Samples taken from the superior mediastinum were sent to pathology for analysis, which confirmed the presence of thymic tissue. Results: Two patients underwent elective total thymectomy due to the gross characteristics of the gland, local 131-I uptake, and high thyroglobulin levels. The remaining three patients had already undergone thymectomy as part of neck dissection during initial surgery, and no further invasive interventions were therefore performed. Pathological examination revealed no metastases in these five patients. Conclusions: Thymus visualization in young patients after administration of therapeutic doses of I-131 seems to be a more common finding than usually thought. Absence of metastasis in the thymus despite high thyroglobulin levels was confirmed in all cases. Based on these results, we suggest that a more expectant and less aggressive therapeutic approach could be used. We also Timo; Captación; Rastreo de cuerpo completo Captación tímica después del tratamiento a dosis elevadas con I-131 en pacientes con carcinoma diferenciado de tiroides: revisión breve de posibles causas y manejo Resumen Objetivos: Descripción de cinco casos de pacientes diagnosticados de carcinoma diferenciado de tiroides (CDT) con captación en el área del timo después de un tratamiento con alta dosis de I-131, y evaluar las posibles causas y manejo terapéutico. Métodos: Presentamos cinco casos de mujeres jóvenes con una edad media de 36,6 años (24---43), que fueron tratadas con una dosis media de 106 mCi de I-131(100---150) que mostraron captación del trazador en las región tímica. Se ralizaron rastreos de cuerpo completo a los 7 días de la administración de la dosis a todos los pacientes, se realizaron imágenes planares de cuerpo completo en proyecciones anterior, posterior y SPECT/TAC de cabeza, cuello y mediastino superior. Valorándose también los niveles de tiroglobulinas con y sin tratamiento sustitutivo hormonal. En todos los casos se confirmó mediante anatomía patológica que la captación visualizada en el mediastino superior correspondía a tejido tímico. Resultados: Dos pacientes fueron sometidas a una timectomía total debido a las características macroscópicas de la glándula, la captación de I-131 y los altos niveles de tiroglobulina. En los otros ...