Figures 1 and 2 show the age distribution of thyroid nodules in the various populations. The greater prevalence of nodules in the younger age group
of exposed Rongelap-Ailingnae people is in contrast to the greater prevalence
in the older age groups in the comparison population. The latter distribution
has been noted in other unexposed world populations (see Table 4, Appendix I).
Figure 3 shows the cumulative percentage of thyroid nodules for the different age and exposure groups over the years. The curve of cumulative increase appears to be leveling off for the Rongelap and Ailingnae groups over
the past decade, as would be expected, since the numbers of unaffected people
are fewer. The Utirik group shows a slight increase.
Sex ratios of thyroid nodules (surgical cases only) were as follows:
Group
Exposed
Total nodules
Benign
M/F
Unexposed*
M/F
10/35
10/28
6/14
2/13
Carcinomas
M/F
0/7
4/1)
As has been noted in other populations of the world, the preponderance
of thyroid nodules was in the females in both exposed and unexposed populations.
In the Marshallese, though the males accounted for a larger fraction
of nodules in the exposed than in the unexposed groups, the reverse was observed for cancer. The number of cases is too small for this finding to be
meaningful. The ratio of benign to malignant lesions for the exposed groups
was 38/7 and for the unexposed 15/5. As pointed out in previous reports, the
radiation exposure may have reduced the cancer ratio in the exposed group
("overkill effect) compared with that in the unexposed group.
(c)
Gross Findings at Surgery
Because of the care taken in clinical examinations, thyroid nodules were
often detected and surgically explored while still quite small. Though many
of these were thought to be single nodules by palpation, most were found at
surgery to be multiple. Thyroid glands were seldom diffusely enlarged. Aside
from the nodules that were present, the remainder of the glandular parenchyma
consistently appeared normal on gross examination.
When pathologically malignant lesions were discovered, they were often
not the nodules that had drawn primary attention preoperatively. In addition
_ to distinct nodules, any areas with gross irregularities were also resected,
no matter how minute.
It is noteworthy that some thyroids, particularly in earlier cases among
the exposed Rongelap group, showed increased numbers of fine tortuous capillaries over the gland surfaces. These resembled thyroids seen in certain
cases of Grave's disease that had been inadequately treated with 131y and were
subsequently treated by thyroidectomy. This feature has not been noted in the
irradiated people from Utirik.
*The Likiep and Wotje groups were not included since they were seen only once.
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