We report the case of 72-year-old woman with mucosa-associated lymphoid tissue (MALT-lymphoma or maltoma) and antibody negative Hashimoto’s thyroiditis. She noted a painless, growing mass in her neck and denied any signs or symptoms of abnormal thyroid function. Her thyroid function test showed no abnormality and thyroid autoimmune antibodies were not detected. The patient underwent a hemithyroidectomy for a growing mass. Histological examination showed diffuse follicular proliferation of small lymphocytes and suggestive of Hashimoto’s thyroiditis. To confirm maltoma, PCR (polymerize chain reaction) was performed and it revealed a clonally rearrangement of the Ig heavy chain gene. We conclude that other factor rather than antigenic stimulation may contribute to unusual histology and development of thyroid maltoma from antibody negative Hashimoto’s thyroiditis.