Ectopic Cervical Thymoma with Myasthenia Gravis and Pure Red Cell Aplasia: A Case Report

Ectopic cervical thymoma is an extremely rare tumor, particularly when associated with myasthenia gravis and pure red cell aplasia.

A 65-year-old female was undergoing treatment for myasthenia gravis and pure red cell aplasia at our hospital. Myasthenia gravis symptoms were controlled with prednisolone, and aplasia was managed using oral cyclosporine A. A gradually increasing cervical mass had been noted previously. Needle biopsy of the mass suggested an ectopic thymoma, and the patient was referred for surgery. Preoperative chest CT revealed a 6.5-cm solid mass within the caudal portion of the left thyroid lobe, which was displacing the trachea to the right. No continuity was noted between the cervical lesion and the thymus. Fluorodeoxyglucose PET showed fluorodeoxyglucose uptake in the mass, with a maximum standardized uptake value of 6.48. No other abnormal uptake was observed, including that in the thymus. The preoperative diagnosis was an intrathyroidal ectopic cervical thymoma associated with myasthenia gravis and pure red cell aplasia. Based on the history of myasthenia gravis, both extended thymectomy and left thyroid lobectomy were performed. The postoperative course was uneventful. Histopathological examination showed that the cervical mass was a type AB thymoma. The examination also revealed an occult type A thymoma (Masaoka stage II) in the thymus.

We encountered a rare case of type AB ectopic cervical thymoma associated with myasthenia gravis and pure red cell aplasia. Extended thymectomy and cervical tumor resection revealed the presence of an occult type A thymoma in the thymus.