eetahe ee B. Mf. Dobyns and B.A. Hyrmer: Thyroid Neoplasms and Hydrogen Bomb Fallout undertaken in this irradiated population and where the possibility of carcinoma was anticipated. minute carcinomas were found. Although the usual reaction might have been to show little concern for such occult carcinomas, this study showsthat when positive lymph nodes were diligently sought, some of these minute primaries had already begun to metastasize. If exploration had not been undertaken until a mass had become conspicuous from outside of the neck. as is the usualclinical scenario. then many additional positive lymph nodes probably would have been found. Pathology The histologic preparations from all of the Marshallese thyroids after 1968 were examined by more than a dozen different pathologists in different medical centers and have been studied by the author (BMD). Dueto difficulties encountered by pathologists in deciding just how manyof these thyroid lesions should be classified as carcinoma, a panel of 6 pathologists, particularly interested in the thyroid, was assembledin 1981 to review the library of microscopic preparations. The panel consisted of: Drs. L.V. Ackerman, W.A. Meissner, D.E. Paglia, J.D. Reid, A.L. Vickery, and L.B. Woolner. The senior author, who had prepared detailed drawings of the surgical findings and had identified the selection of tissues for histological preparations, attended these sessions. During these sessions there were subtle differences of opinion as to whether a lesion should be classified as carcinoma or considered an atypical adenoma [17-19]. In 1 case there was debate concerning a metastatic deposit in a lymph node, althoughall of the lesions in the gland were thought to be benign. Even though gross thin serial sections had been madeto find the very minute primary in this case, there was speculation that the primary had been missed. Unanimousopinion was obtained in most cases (Table 3). Altogether there were 23 cases considered byall of the panel to contain at least one carcinoma. Among the 245 individuals known to have been exposed (excluding those in utero) on the 3 atolls, there were 55 operated upon (Table 2). In 16 patients there were malignant lesions and in 39 patients there were benign lesions. Among 668 unexposed Rongelap controls, 12 persons had or developed masses and underwent surgery. In 4 patients, carcinomas were found; in 6 patients, benign adeno- mas; and in 2 patients, atypical adenomas. Masses were found in 2 of 473 unexposed people of Utirik origin. One was a carcinoma; one was an atypical adenoma. Among 354 people whose thyroids were examinedon “‘street surveys’’ on several atolls (primarily Likiep and Wotje), 8 people were found to have masses and were explored; 2 were carcinomas, 4 were atypical adenomas, and 2 were benign adenomas. These people were considered to have been outside ofthe high risk area according to the aerial surveys made the day of the accident (Table 2). Mostof the frank carcinomas (Fig. 3) were mixed papillary and follicular (19 cases). By most classifications these would all have been called papillary carcinomas [20]. The follicular component predominated in most cases. In 5 cases the lesion was almost exclusively follicular. Three cases were predomi- nantly papillary and | case wassolid cellular. 131 Atypical Lesions In the final analysis it. seemed important to make a separate category called ‘atypical adenomas”’. These small cytologically atypical hyperplastic lesions ranged from a few millimeters to several centimeters in diameter. At least one or more pathologists (but a minority) had originally considered some of these lesions to be carcinomas. They were found in the most heavily exposed individuals and frequently in glands that often contained a carcinoma. There were 13 cases in which no carcinoma was present (Table 2). Such an association suggested that the same factor that produced these atypical lesions also produced carcinomas. The features of the cells in such lesions seemed to imply that with further growth, the lesion might display diagnostic features of carcinoma, as suggested by others (21, 22] who studied thyroids exposed to roentgen radiation (Figs. 4 and 5). These ‘changes were found even though supplemental thyroxine had been given. Autoradiographs were done onall operative cases and showedthat these lesions took up verylittle or no radioiodine, as occurs with most all carcinomas[12]. Ruling out malignancy in someof the larger atypical growths proved to be difficult (Fig. 6). In some of these lesions the finding of a mixed papillary and follicular pattern with crowding of cells, bearing bizarre nuclear forms with vacuolation and possible mitoses prompted a suspicion of a potential to metastasize (Figs. 4B, 6C, 7 and 8). However, without clear evidence of invasive qualities, such as capsular, blood vessel or lym- phatic invasion, such a diagnosis wasnot possible. Still, this did not eliminate a suspected potential to become invasive with the passage of time. Multiple Malignant Lesionsin the SameIndividual Amongthe 23 patients with malignantlesions of the thyroid. 16 patients showed additional benign and or atypical adenomatous lesions. In 10 patients there were multiple carcinomas. In 8 patients a smaller carcinoma was found in the opposite lobe (Fig. 2). Although there is the possibility that the additional carcinomas could have represented intraglandular spread, it 1s much more likely that they represented multicentric sites of origin because the entire gland was at risk from radiation. However, 4 of the 10 patients with multiple carcinomas were among those persons considered to be unexposed. These observations of multiple carcinomas emphasize the importance of removing all thyroid tissue completely when a carcinoma is found following radiation exposure, It should be assumed that other subclinical carcinomas may be present in the same gland, even though at surgery gross nodularity does not appear to be present in other parts of the gland. Re- Operations Three exposed persons from Rongelap who had previously undergone bilateral subtotal thyroidectomy ultimately developed additional discrete growing masses 10 or more yearsafter the first operation. All 3 patients had shown atypical adenomas at the first operation. Total or very near total thyroidectomy was done at the second operation. A new lesion in 2 cases