[Primary lymphoma of the thyroid--diagnostic and treatment problems. The case report].

The authors present the case of primary malignant thyroid lymphoma and problems with distinguishing between Hashimoto's thyroiditis and primary thyroid lymphoma. Primary malignant thyroid lymphoma (PMTL) is a rare disease and difficult to diagnose. The appearance of PMTL may be preceded by Hashimoto's thyroiditis. The biopsy is useful but often only surgical treatment allows to establish diagnosis. The treatment of PMTL includes surgical treatment, chemo- and radiotherapy. The prognosis depends on the disease period.