Histologic definitions:
In interpreting the
program
data
on
Brookhaven
thyroid
Appendix D lists all exposed persons who have
had thyroid surgery which confirmed a thyroid
lesion.
medical
nodules
the
histopathological classification of thyroid nodules
used by the expert panel of pathologists needs to
be reviewed.
This classification, based on
diagnostic categories recommended by the World
Thyroid nodules in the Comparison group:
The examination of the Comparison group has
been invaluable in interpreting the thyroid nodule
risk data among the exposed population. Even
though they do not constitute an ideal "controi"
group, it is not likely that a better comparison
population could have been obtained without
initiating a formal, prospective research effort. It is
appropriate that the voluntary cooperation of the
Heaith Organization (Hedinger and Sobin, 1974)
and modified in 1981 by Dr. Donald Paglia of the
Department of Surgical Pathology, University of
California, Los Angeles, for the panel’s use, has
been applied to all thyroid specimens obtained at
surgery since the beginning of the program:
Adenomatous nodule: a focal proliferative lesion
consisting of changes typical of adenomatous
goiter; the lesions are hyperplastic and do not
fulfill criteria of true neoplasms.
Adenoma: an encapsulated proliferative lesion
with a uniform internal growth pattern and benign
clinical course.
Occult papillary carcinoma:
a small
nonencapsulated sclerosing carcinoma; considered
to be clinically benign even if associated with
positive regional lymph nodes.
Papillary carcinoma:larger, infiltrating carcinoma,
usually containing both papillary and follicular
components.
The four pathologists on the panel that review
the Marshallese specimens are: Dr. L.V.
Ackerman, Health Sciences Center, SUNY,Stony
Brook, NY; Dr. W.A. Meissner, formerly with
New England Deaconess Hospital, Boston, MA;
Dr. A.L. Vickery, Massachusetts General Hospital,
Boston, MA; Dr. L.B. Woolner, Mayo Clinic,
Rochester MN.
Histologic sections of all
surgically removed thyroid tissue have been
examined by these authorities. Although most
diagnoses have been unanimous, some were
controversial.
In the following analysis and
discussion of Marshallese nodules, the “most
neoplastic” diagnosis has been selected when there
has been a split decision, with the "least
neoplastic” being the adenomatous nodule, next
being the adenoma, the third being occult
papillary cancer, and the most neoplastic being the
carcinoma.
members of this group be gratefully acknowledged
by all who have relied on the Marshallese thyroid
nodule data to interpret the role of radiation in
causing thyroid disease. In that the unexposed
Comparison group comprises persons of Rongelap
ancestry and was quite closely age- and gendermatched whenselected in 1957, this group is more
representative of the exposed Rongelap population
than any other Marshallese community and certainly
more so than a population of non-Marshallese.
The development of thyroid nodules in the
Comparison population is similar to the
spontaneous thyroid nodule incidence reported
elsewhere. Maxon et al. (1977) concluded that the
rate of development of benign thyroid nodules and
thyroid carcinomas in western countries is 0.07%
and 0.01% of the population per year, respectively,
and that the incidence is linear with respect to age.
In 1990 the numberof person-years of observation
of the Comparison group was 10,400. Therefore,
based on the conclusions of Maxonetai. (1977), the
expected number of thyroid nodules, benign and
malignant, would be 8.3, of which 6 or 7 would be
benign and 1 or 2 would be carcinomas.* In fact, 8
nodular thyroids were detected, of which 6 were
benign and 2 were carcinomas (see Table 2).
Possible sources of inaccuracy include the following:
(1) Only surgically confirmed nodules are included.
Therefore, since several unoperated nodules have
been diagnosed in the Comparison group, the
“observed” number may underestimate the true
numberof thyroid nodules. However, the palpated
nodules may have been lipomas or neuromas, for
example, and therefore appropriately excluded. (2)
One of the two occult papillary carcinomas
diagnosed in this group was not detected prior to
surgery. This "nodule" is therefore excluded. Thus
the total number of nodules is given as 8 rather
than 9, as listed in Table 2. (3) 1984 is the latest
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