[Show abstract][Hide abstract] ABSTRACT: A 12-year-old boy with T-cell ALL was found to have occult papillary thyroid carcinoma at autopsy. This patient was treated with chemotherapy but no radiotherapy was utilized. Family history was not contributory. Because of short latent period (14 months) and no history of radiotherapy, an intrinsic factor might have played a major role in developing this second malignancy. Currently 11 solid tumors have been reported as second malignant neoplasms after ALL in childhood. Four (including this case) of 11 were thyroid carcinoma. Two of them did not receive any radiotherapy. Special interrelation between ALL and thyroid carcinoma may be considered. And this interrelation should be taken into account in following the patients with ALL in the future.