Morphological characteristics of human mast cells in normal and pathological thyroid glands. Functional aspect of human mast cells in comparison with rat mast cells

Abstract

We examined the distribution and population density of human mast cells in thyroid glands. The results were compared with those of Sprague-Dawley (SD) rats because they thyroid function of SD rats is known to be under the control of bioactive amines discharged from mast cells. Normal thyroid tissues were obtained either form autopsy or from a normal portion of the tissue distant from nodular lesions. Thyroid tissues were surgically removed from cases of Graves' disease and other tumorous lesions such as follicular adenoma, follicular carcinoma, papillary carcinoma and medullary carcinoma. The tissues were fixed with buffered formaldehyde or Carnoy fluid and embedded in paraffin. Mast cells were stained with toluidine blue and naphthol ASD chloroacetate esterase (esterase). Immunoperoxidase reactions to antihuman tryptase and chymase monoclonal antibodies were then observed. The mast cells were also observed by electron microscopy. The histamine content of the thyroid tissues was estimated by the high-performance liquid chromatography method. The mast cells in SD rat thyroid glands were scattered in perifollicular connective tissues which were comprised of capillaries, fibroblasts, nerve fibers and occasional fine deposits of collagen fibrils. Their cytoplasmic granules appeared to be distinct, electron dense and amorphous. In contrast, the mast cells in normal human thyroid glands were scattered exclusively over relatively thick interstitial spaces like the interlobular and subcapsular connective tissues. These mesenchymal tissues were composed of bundles of collagen fibrils, fibroblasts, histiocytes and thin cytoplasmic processes of unknown origin. In pathologic thyroid tissues, the mast cells were distributed in a similar pattern over the connective tissues.(ABSTRACT TRUNCATED AT 250 WORDS)