Mucosa-associated lymphoid tissue (MALT) lymphoma of the thyroid: report of a case.

The patient was 59-year-old Japanese woman who presented with a neck swelling. Ultrasonography and computed tomography demonstrated a round tumor in the thyroid right lobe measuring 2.5 x 1.5 cm in size. A right hemithyroidectomy with lymph node dissection was performed. Histopathological findings demonstrated low-grade B cell lymphoma of the mucosa-associated lymphoid tissue (MALT) associated papillary microcarcinoma. A previous report showed an excellent prognosis of MALT lymphoma of the thyroid without capsular invasion or lymph node involvement. We also describe the concept of MALT lymphoma as a primary lesion in which lymphoid tissue is not present in the normal state.