The solid ceilular Lesions are :nore inclined to arise in follfcies whicn are
similar to the normals in size. A site of cellular proliferation oqcurs in the follicular wall.
As many as 50% of the cells forming a tiny mass of pe haps a dozen cells
are labelled with the “H-TdR label showing that within the 4 hours|before sacrifice
many of the cells were picking wp tritiated thymidine in preparatign
for mitosis.
Before the relatively small follicle is filled with cells, some ofthe cells bearing
the “H-TdR label are fod outside of the basement membrane of the] follicle. These
apparently rapidly proliferating cells appear to be spreading to fbrm a solid
cellular mass.
Some of these lesions are partly encapsulated but femnants of what
appear to be partial encapsulation are seen in the tumor mass.
Sp ead of the neo-
les may be found
plasm beyond the true thyroid capsule ultimately may be found.
where the 34-TaR label is moderate, but at the point where the lesfion has breeched a
thyroid capsule and spread into surrounding fat, the “H-TdR labellfing
margin of cells in greatly intensified.
in the advancin
|
Rats, particularly the Long-Evans strain as used by Lindsay
Chaikoff and
associates are prone to develop spontaneous neoplasms composed of fi
or C-cells as animals age.
The neoplasms form solid masses of ce
rat may be confused with the solid lesions arising from the folli
rats also show considerable hyperplasia of C-cells which may be a
“neoplasms.
In our early experience we could not distinguish be
lesions and considered them all'Solid cellular’ We intially as
wrongly) that C-cell tumors did not represent a significant mmbeq
of the neoplasms
in our irradiated rats because the solid cellular lesions were ve¥y
uncammon among
controls in our particular strain of Sprague-Dawley rats.
The fajlure to be able to
identify which solid cellular lesions were of C-cell origin and
cell origin not only left our analysis of the incidence of the
ich were of follia
types in question
but also weakened our hypothesis that most of the solid lesions were of follicular