The contribution of the Study of the Marsnz”"sse in our Laforatory The Marsha*lese materials are of great importance to the study er this contrac? The fresh tissue when removed here by us is studied sremptly by meth@ds in use under this contract. Although most of the neoplasms found in the Marshallfse have been benign, it is important to note that a total of 6 carcinomas have begén of these had metastasized tc the regional cervical 1j;=>h nodes. found. Two Thefradiated Marshals. thyreids ofter. ave many minute solid cellular or mixe< papillary ang follicular lesic?: in addition to = much larger lesion which had drawn srimary attentioh. Many of the tiny lesions are occupying an area no larger than a icren normal follicles just as is seen in the raccated rat thyreids. At the time of the last annual report we descrite= a 21 year olf Marshallese who we had Just operated for mitiple benign adenomas. mother was exposed to fallout. = was 6 months fin utero when his The special studies c= that thyroid Fissue showed the bizarre nuclear forms recognized as evidence of radciezion effect. the time of preparation of this report, we have just operated arn< removed several benign but atypical adencras from the thyroid of his mother wnc =ad developed masses in the last year. The facter of long delay in the development of =eoplasms is animals and me... Our experience has shown that the rets do not deve Dhasized in both they are radiated when very young and 1/2 to 2/3 of <he life span ps Marshallese lesion did not develop for 9 years. Mar; of the early Jesions~came from the atoll with the highest fallout (Rongelap). It was quite some lesions began appearing in people who were on the nex= nearest ato the dose had been somewhat less. While lesions were appearing on ydars later that no lesions, buc in the most recent years, 8 individueis have been ope ated and 3 car cinomas found. These observations seem to emphasize =he risk of th low dose range. Further support for the concern for the low dose and long latest period is illustrated by the very considerable number of individuais coming to megical attention for neoplasms of the thyroid after irradiation to tie head and neck} Relatively small doses to shrinx lymphoid tissue and even smaller doses for acne seem implicated in our experience amé that of others. We are screening a very considerable number of persons referred because” of such known exposure. The Part Played by TSH in Neoplasm Formatic. Following131y Radiation Although each rat experiment has required almos= 2 ers laps succeeded in cStaining neoplasms in rat thyroids usinz _ frequency. 1t alane The yields have become (60%) sufficient. good so that be used to test inhibiting and stimulating effects =. the inductiar lesions. time, we have With increasing [the model may now and growth of sucr For. many years thyroid stimilating hormone (iS&5 has theorectjcally been implicated in the cevelopment of thyroid tumers. First =. the chronic dpplication of an iodine deficient diet; then ry the chronic use of gexicrogenic subs#ances and finally in recent years by radioiodine. Simply stated, the Lack of iodine[to make hormone, the block of the synthesis of hormone or the damage => the cell mechanism for hormone producticn may lead to a deficiency of thyroi¢ normone and a gompensatory increas: