[Differential diagnosis of Hashimoto's thyroiditis from thyroidal neoplastic diseases]

Thyroid lymphoma is a relatively rare disease, but has attracted the attention of many investigators because of its putative relationship with Hashimoto's thyroiditis. The definite diagnosis of thyroid lymphoma, especially the histologic distinction from small cell carcinoma or Hashimoto's thyroiditis, has been problematical and even regarded as impossible during the past decades. Recent progress in immunological methods including molecular biology has resolved many of the diagnostic problems in this field, thereby providing a scientific basis for approaching these diseases. In this review, we have discussed the important role of Hashimoto's thyroiditis in the etiology of thyroid lymphoma; the B-cell nature of proliferating cells in thyroid lymphoma; the histologic differential diagnosis.