Papillary thyroid carcinomas from young adults and children contain a mixture of lymphocytes.

The immune response appears to be important in preventing metastasis and recurrence of thyroid cancer. We previously showed that papillary thyroid carcinoma (PTC) from children and adolescents that contain the most numerous proliferating lymphocytes have the best prognosis. However, the types of lymphocytes involved are not yet known. To further define this, we examined 21 PTCs from patients 21 yr of age or younger (52% were 18-21 yr of age) for the presence of CD4+ (helper), CD8+ (killer), CD19+ (B cells), and CD56+ (natural killer) cells as well as proliferating lymphocytes (Ki-67+). Nearly half the PTCs contained CD4+ (9 of 21, 43%), CD8+ (8 of 21, 38%), or CD19+ (10 of 21, 48%) lymphocytes. Only one PTC (1 of 21, 5%) contained CD56+ lymphocytes, and none contained all four cell types. By dual staining, none of these lymphocytes were proliferating (Ki-67+). However, PTCs containing either CD8+ cells (n = 8) or a combination of CD4+, CD8+, and CD19+ cells (n = 5) contained more numerous proliferating lymphocytes than did PTCs containing any other combination (14.2-fold increase, P = 0.03 and 13.1-fold increase, P = 0.003, respectively). During follow-up, none of the PTCs containing either CD8+ lymphocytes or the combination of CD4+, CD8+, and CD19+ lymphocytes recurred. However, the cohort is too small and the follow-up inadequate to provide accurate information on the clinical impact of these immunological findings. We conclude that the immune response against PTC is important and also complex, involving more than one type of lymphocyte.