Concurrent myasthenia gravis-related cervical thymoma in a patient with diffuse large B-cell lymphoma: a case report 

BACKGROUND: Cervical thymoma is a rare thymic epithelial neoplasm. Evidence supports an increased risk of second primary malignancies in patients with thymoma. We report a rare case of a patient with synchronous cervical thymoma and diffuse large B-cell lymphoma. CASE PRESENTATION: An 81-year-old Thai woman was referred for further treatment of diffuse large B-cell lymphoma at Siriraj Hospital, Bangkok, Thailand. While waiting for a review of the original pathological examination of a mass in the left neck and a mass in the left arm, the attending physician noticed ptosis of the upper eyelids, which was proven to be caused by myasthenia gravis. The final pathology review confirmed that the arm mass was diffuse large B-cell lymphoma, but the neck mass was cervical thymoma, type B1, not diffuse large B-cell lymphoma. Interestingly, the patient reported that the arm mass had been present for 2 years, while the neck mass had grown rapidly in the past month. A diagnostic challenge had arisen when the initial morphological evaluation was not performed with care, causing the first pathologist to misinterpret that the neoplastic cells in both masses were the same. CONCLUSION: Concurrent cervical thymoma and diffuse large B-cell lymphoma were proven after a careful pathology review, leading to better clinical management.