Clinical presentation: A 78-year-old woman was referred for evaluation of a newly discovered lump in the right side of the neck. The lesion developed within 3 to 4 months.

Palpation: a hard, almost fixed tumor in the right lobe.

Functional state: euthyroidism (TSH-level 4.09 mIU/L).

Ultrasonography. There was a large and several smaller, irregular, hypoechogenic lesions in the right lobe. The vascularization was decreased.

Cytology: suspicion of non Hodgkin' lymphoma.

Biopsy was performed from the right thyroid and histopathology revealed large B cell lymphoma.