Not just a neck mass: Primary thyroid diffuse large B-cell lymphoma

Primary thyroid lymphoma (PTL) is a rare thyroid malignancy, most often associated with chronic autoimmune thyroiditis. We report the case of a 40-year-old woman with a history of hypothyroidism treated with levothyroxine, who presented with a rapidly enlarging anterior neck mass accompanied by progressive dyspnea, dysphagia, and dysphonia. Physical examination revealed a large, firm goiter fixed to deep planes, with overlying inflammatory skin changes. Laboratory tests showed anemia, lymphocytosis, elevated thyroid-stimulating hormone (TSH), positive anti-thyroid peroxidase (anti-TPO) antibodies, and markedly increased lactate dehydrogenase (LDH). Imaging revealed diffuse thyroid enlargement with mediastinal extension, tracheal deviation, and invasion of the larynx. Due to worsening compressive symptoms, the patient underwent urgent decompressive surgery with intraoperative biopsy. Histopathological and immunohistochemical analysis confirmed the diagnosis of diffuse large B-cell lymphoma (DLBCL) of the thyroid. She received four cycles of R-CHOP chemoimmunotherapy, resulting in rapid clinical improvement and normalization of inflammatory and tumor markers. At 8-month follow-up, the patient remained in remission. This case highlights the importance of considering PTL in the differential diagnosis of rapidly enlarging thyroid masses, particularly in patients with autoimmune thyroid disease. Prompt diagnosis through appropriate histological assessment and early initiation of systemic therapy are critical to improving prognosis and preventing life-threatening airway compromise.