Clinical data: a 92-year-old woman has been treated for hypothyroidism for 3 years. Her relatives had been taking notice of a gradual increase of the left lobe for 6 months. At the time of the investigation the hasn't been able to swallow solid foods.

Palpation a large, hard tumor in the left lobe.

Functional state: euthyroidism on daily 75 microgram levo-tiroxine (TSH-level 3.08 mIU/L).

Ultrasonography: the right lobe was hypoechogenic corresponding to the underlying Hashimoto's thyroiditis. There was a huge tumor in the left thyroid. The pattern of the left lobe varied from moderate to severe hypoechogenicity. The tumor was avascular.

Cytology: suspicion of non Hodgkin' lymphoma.

Biopsy was performed from the left thyroid and histopathology revealed MALT-type non Hodgkin lymphoma.