Non-Hodgkin's lymphoma followed by plasmacytoma, both arising in A thyroid gland with Hashimoto's disease.

We describe here a rare case of malignant lymphoma followed by plasmacytoma in Hashimoto's thyroiditis. The patient developed malignant lymphoma (small, non-cleaved cell, and non Burkitt's type by Working Formulation classification), and remained in remission for 2 years after receiving combination chemotherapy, and then developed plasmacytoma in the same lesion. Rearrangement bands for IgH from both specimens showed different bands, indicating that both were of monoclonal type but of a different clonal origin. Considering the clinical course in this case, thyroidectomy may be indicated for lymphoproliferative diseases in Hashimoto's thyroiditis treated with chemotherapy.