Background: Primary thyroid mucosa-associated lymphoid tissue (MALT) lymphoma is an uncommon extranodal B-cell lymphoma and a rare cause of thyroid enlargement. Diagnosis is challenging when initial cytological findings are inconclusive, as preoperative investigations may fail to distinguish lymphoma from other thyroid pathologies, often resulting in an unexpected diagnosis confirmed only after histopathological evaluation. Objective: To highlight the importance of considering lymphoma in the differential diagnosis of progressive thyroid masses, through the clinical presentation, diagnostic challenges, pathological characteristics, and management of a patient with primary thyroid MALT lymphoma. Methods: Clinical, radiological, operative, histopathological, and immunohistochemical data were retrospectively reviewed from the patient's medical records to characterise the diagnostic pathway and clinical course, including perioperative findings, postoperative complications, and follow-up outcomes. Results: A 70-year-old woman presented with a progressively enlarging neck mass over one year, with dysphagia and reduced oral intake. She had initially presented in 2023 with mild thyroid enlargement; FNAB at that time showed findings consistent with Hashimoto's thyroiditis. Following progressive enlargement, total thyroidectomy was performed. Histopathology revealed MALT lymphoma with focal areas suspicious for large-cell transformation, and immunohistochemistry confirmed low-grade B-cell non-Hodgkin lymphoma of MALT type. Postoperatively, the patient developed bilateral vocal cord paralysis with airway compromise, managed with arytenoidectomy and satisfactory airway improvement. Conclusion: Primary thyroid MALT lymphoma should be considered in patients with a progressive thyroid mass, particularly when clinical progression is inconsistent with cytological findings.