PROGNOSTIC IMPACT OF THYROID LYMPHOCYTIC INFILTRATION IN PATIENTS WITH MEDULLARY-THYROID CARCINOMA

A retrospective search for lymphocytic infiltration of the thyroid was performed on archival paraffin specimens from 95 cases of thyroid med ullary carcinoma observed at a single institution during a 30-year per iod. A mild lymphocytic infiltration of the nonneoplastic thyroid tiss ue, mainly concentrated at the edge of the tumor mass, was observed in 33 cases, while in a further 24 cases a moderate to marked lymphocyti c infiltration, resembling that seen in chronic lymphocytic thyroiditi s, was homogeneously distributed all over the gland, with no apparent relationship to the site of the primary tumor. Virtually no lymphocyti c infiltration was detected inside of any of the tumors. The presence of chronic lymphocytic thyroiditis seemed to be a characteristic of th e host rather than a tumor-induced event. Statistical univariate analy sis of relapse-free survival and overall survival showed that lack of chronic lymphocytic thyroiditis marked those patients with an increase d risk of disease recurrence and death. However, the observed risk for survival was statistically nonsignificant, whereas that for disease r ecurrence was significant and remained in a multivariate model of stat istical analysis.