Synchronous primary ectopic intrathyroidal thymoma and papillary thyroid carcinoma: double trouble: a case report

Thymomas are typically located in the anterior mediastinum. Primary ectopic intrathyroidal thymoma are exceedingly rare, with only nine cases reported in the English literature. Papillary thyroid carcinoma represents the most common type of thyroid carcinomas, accounting for almost 80% of cases. Herein, we present the first case reported in the literature of primary ectopic intrathyroidal thymomas occurring synchronously with a papillary thyroid carcinoma. We aim to discuss its clinical, morphological, and immunohistochemical features, and highlight the diagnostic challenges posed by this exceptional coexistence.

A 62 year-old North African woman, with no past medical history, presented with a cervical nodule. Cervical ultrasound showed an encapsulated, firm nodule measuring 7 × 5 × 3 cm in the right lobe and a 0.8 cm nodule in the left lobe. Thyroid function and calcium test results were within normal limits. The patient underwent total thyroidectomy. Microscopic examination and immunohitochemical study concluded that there was a primary ectopic intrathyroidal thymoma in the right lobe and a papillary thyroid carcinoma in the left lobe. The postoperative course was straightforward. Given the presence of synchronous papillary thyroid carcinoma, the patient received adjuvant radioactive iodine therapy and remains alive 2 years postoperatively.

Primary ectopic intrathyroidal thymomas are exceedingly rare, with only nine cases previously reported in the literature. Given the nonspecific clinical and radiological presentation, definitive diagnosis relies on pathological examination. Establishing the diagnosis might be challenging given the wide array of potential differential diagnoses. Accurate identification and exclusion of differential diagnoses are essential for appropriate patient management. The coexistence of primary ectopic intrathyroidal thymoma and papillary thyroid carcinoma appears to be incidental.