Primary Intrathyroidal Non-Hodgkin Lymphoma: A Case Report

Primary thyroid lymphoma (PTL) is a rare disease characterized by the appearance of a rapidly growing solid mass in the cervical region. A major risk factor is chronic autoimmune thyroiditis with lymphocytes infiltrating the thyroid gland. The lymphoproliferative disease is seen more frequently in the females. PTL usually develops in the sixth and seventh decades of life. We present a case of a 66-year-old woman with diffuse primary B-cell thyroid lymphoma with no prior evidence of underlying autoimmune thyroid pathology. The initial localization of the lymphoproliferative disease was in the thyroid gland, but the involvement of regional cervical lymph nodes was also found at the time of diagnosis. After histological verification with immunohistochemistry and staging by imaging, chemotherapy was initiated according to the R-CHOP (rituximab, cyclophosphamide, hydroxydaunorubicin hydrochloride, Oncovin^® (vincristine), prednisone) protocol. An excellent therapeutic response was achieved with lymphoma remission after six cycles under the mentioned protocol. Thyroid autoantibodies became positive 18 months after rituximab treatment, possibly reflecting the transient suppressive effects of the immunotherapy. The patient was subsequently kept followed up by a multidisciplinary team in the light of possible lymphoma recurrence and/or development of thyroid dysfunction. This case report demonstrates possible challenges for the diagnosis, treatment, and follow-up of this rare thyroid lesion. At the time of diagnosis, the clinical presentation of the disease, the ultrasound image, and the cytological result may be similar to other low-grade thyroid carcinomas or secondary metastatic involvement of the gland. The initial lack of underlying thyroid autoimmunity makes this distinction even more challenging. Furthermore, despite the rapid resolution, regular long-term monitoring for recurrence is required.