[Intrathyroidal thymus can cause confusion in the diagnosis of a thyroid mass. A case report]. / Timo intratiroideo: una causa de confusión en el diagnóstico de masas tiroideas infantiles. Reporte de caso.

Intrathyroidal thymus tissue (ITTT) is a rare, benign condition; its diagnosis can prove challenging due to unfamiliarity with this entity. However, it has ultrasonographical and cytological characteristics which can suggest its presence and thus should be considered in the differential diagnosis of thyroid nodules. Presently, immunohistochemistry can be used with fine needle aspiration (FNA) cytology, thus decreasing the need for unnecessary surgery. We discuss the usefulness of immunohistochemistry in thyroid cytology, with reference to a case of a 10-year-old patient, who underwent partial thyroidectomy for a suspicious thyroid nodule which was eventually diagnosed as ITTT by the histopathology of the surgical specimen.