Scanning electron microscopic study of the collagen sheath of the human thyroid gland and its disorders
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Insights
The study reveals distinct collagen sheath structures in human thyroid disorders using scanning electron microscopy (SEM). These perifollicular sheaths show unique collagen compositions and arrangements in various benign and malignant thyroid conditions.
Area of Science:
- Histology
- Pathology
- Biomaterials Science
Background:
- The collagenous perifollicular sheath of the human thyroid gland plays a role in follicular structure.
- Understanding its composition and alterations in disease is crucial for diagnosis.
Purpose of the Study:
- To characterize the collagenous perifollicular sheath in normal and diseased human thyroid glands.
- To differentiate thyroid pathologies based on perifollicular sheath morphology.
Main Methods:
- Cell-maceration and scanning electron microscopy (SEM) were utilized.
- Detailed morphological analysis of collagen bands and fibrils in perifollicular sheaths.
Main Results:
- Normal thyroids exhibit spherical sheaths with thick bands and fine fibrils.
- Benign diseases show variations in size/shape but similar composition.
- Adenomas and carcinomas display altered sheath composition (predominantly fine fibrils) and structural changes like holes.
- Carcinomas exhibit specific patterns: papillary in papillary adenocarcinoma, well-developed in medullary carcinoma.
Conclusions:
- Perifollicular sheath morphology, particularly collagen composition and presence of holes, can distinguish between normal, benign, and malignant thyroid conditions.
- SEM provides valuable insights into the structural basis of thyroid disorders.
Abstract:
A cell-maceration/scanning electron microscope (SEM) method was employed to demonstrate the collagen sheath around follicles (perifollicular sheath) of the human thyroid gland and its disorders. In the normal thyroid gland, the follicles were surrounded by spherical collagen sheaths composed of a framework of thick collagen bands 1-5 microns in width and fine solitary collagen fibrils 50-70 nm in diameter. In benign thyroid diseases (Graves' disease, Hashimoto's thyroiditis and adenomatous goiter), the perifollicular sheaths differed in size and in shape according to the disease, but they were always composed of thick collagen bands and fine fibrils as in the normal thyroid. On the other hand, the spaces surrounded by the perifollicular sheaths varied markedly in size in follicular adenoma, were small in oxyphilic adenoma, and irregularly shaped in embryonal adenoma. In all these adenomas, the perifollicular sheaths were mainly composed of fine fibrils 35-45 nm in diameter. In follicular carcinoma, the size and shape of the space surrounded by the perifollicular sheaths were irregular. In papillary adenocarcinoma, the collagen sheaths showed a papillary pattern. In medullary carcinoma, tumor nests were surrounded by well developed collagen sheaths. In all these carcinomas, the collagen sheaths were mainly composed of fine collagen fibrils 32-45 nm in diameter. In adenomas and follicular carcinoma, the perifollicular sheaths frequently had large holes through which the spaces surrounded by the collagen sheaths connected to each other. Such holes were, however, rare in the normal thyroid and benign non-neoplastic thyroid diseases.
