-21microns external diameter) in several irradiated organs.
The lesion
was described as a plaque-like thickening of intima due to collection
of foam cells alone or foam cells mixed with various other cells, fluid,
fibrin or hyaline material, between endothelium and internal elastic
membrane.
Although pathological changes were found sometimes also in
adjacent internal elastic membrane, media and adventitia, these structures
were often normal.
of fhumen.
The plaque may cause marked narrowing or even occlusion
Thrombosis, fibroblastic proliferation of deposition of elastic
tissue in the thickened intima seldom result.
The foam cell plaques
“were found in small arteries in organs subjected to radiation therapy
(large doses) by roentgen rays and/or gamma rays from radium sources.
The paper states that the plaques probably result from migration of
lymphocytes and monocytes into the intima from the blood stream and
subsequent transformation (meaning differentiation or metamorphosis)
of these cells into foam cells by their ingestion of lipids which have
been freed by the dissolution of red cells in the intima or which have
accumulated in the intima efter passage across portions of the endothelium
that was rendered more permeable than normal by irradiation.
The paper
contained a casual or incidental statement to the effect that the foam
cell plaques in irradiated small arteries closely resemble the
early lesion of atherosclerosis.
If this were true, it would be
indicative of some of the kinds of changes which may occur in vessels
before, and presumably responsible for, subsequent deposition of
calcium,
It is interesting to point out, however, that earlier in
this paper, Sheehan indicated that foam cell plaque was an uncommon
or at least rarely described lesion,