Non-hodgkin lymphomas of the thyroid.

Twenty-nine cases of non-Hodgkin lymphomas presenting in the thyroid were classified according to Rappaport and Lukes and Collins. In the Rappaport classification there were 19 histiocytic, three mixed, five nodular PDL and two undifferentiated lymphomas. According to Lukes and Collins, 21 cases were follicular center cell lymphomas, eight were immunoblastic sarcomas. Cases classified as histiocytic according to Rappaport fell into the immunoblastic sarcoma and large cleaved or non-cleaved follicular center cell lymphoma groups. Immunoperoxidase studies confirmed the B cell nature of some of these cases. Survival was dependent on clinical stage, but this appeared to reflect the predominant cell type. Thus, follicular center cell lymphomas of the large non-cleaved type presented predominantly in stage I, while immunoblastic sarcoma was mostly stage IV and tumors of the small cleaved follicular center cell (FCC) type had excellent survival despite a usual presentation in stage IV. It is concluded that probably only lymphomas of the large non-cleaved FCC type and immunoblastic sarcoma (IBS) occur as true primary thyroid tumors, while small cleaved FCC lymphomas most likely represent systemic disease when first presenting in the gland. The median survival for large non-cleaved lymphomas in stages I and II was 31.5 months compared to 5.5 months for stage IV IBS. Although strongly suggestive these correlations were not statistically significant. An association with severe chronic lymphocytic thyroiditis was observed in 22 cases, including all cases of immunoblastic sarcoma as well as nine of ten large non-cleaved follicular center cell tumors. The prognostic significance of the Lukes-Collins classification is discussed in relation to these examples of thyroid lymphoma. [ABSTRACT FROM AUTHOR]