Colloid Degeneration

Colloid degeneration is, strictly speaking, a subspecies of hyaline degeneration (see), since colloid is the name given to certain hyaline products secreted by epithelial cells, mainly the epithelium of the thyroid gland and the posterior part of the anterior lobe (the so-called pars intermedia) of the pituitary gland. The term "colloid" was introduced into pathology by Laennec, who wished to highlight the peculiar consistency of this substance, which resembles a semi-liquid glue or jelly, and it should not be confused with the corresponding chemical term. Morphologically, colloid is completely homogeneous and structureless; this homogeneity is not disrupted even after treatment with alcohol or acetic acid (unlike mucus). Like all hyaline substances, colloid is strongly stained by acid dyes (eosin, fuchsin); however, according to the van Gieson method, unlike the hyaline of connective tissue, it is stained mostly yellow. Upon prolonged residence in the body, the tinctorial properties of colloid masses (as well as their consistency) can change significantly, due to which, even on a single specimen, their coloration in different places often turns out to be uneven. By their chemical composition, colloids of various origins are far from homogeneous and do not yield any specific microchemical reaction. For typical colloid, i.e., the colloid of the thyroid gland and the pituitary gland, only the content of iodine in it is characteristic. Colloid is a secretory product of epithelial cells and, according to some observations, is formed already ready-made in the cell in the form of droplets, which are then released into the lumen of the glandular cavity; according to others, the cell produces only a pre-stage of colloid in the form of peculiar acidophilic granules, which turn into a colloid substance only after release from the cell and dissolution in the tissue fluid. Sometimes in pathological cases, a complete colloid transformation of the cellular protoplasm occurs with the displacement of the nucleus to the periphery, its compression, and subsequent disintegration and death of the cell. Under the name of colloid degeneration, it is customary to understand any excessive accumulation of this substance in glandular or cystic cavities, regardless of whether it was formed by the usual secretory pathway, or by way of complete colloid transformation of cells, or, finally, due to its obstructed outflow. The main sites of such pathological accumulation of colloid substances are 1) the thyroid gland in so-called colloid goiter, 2) the pars intermedia of the pituitary gland, and 3) certain cancers, adenomas, and adenocystomas (mainly those that develop in the thyroid gland and in the ovaries, and their metastases). A similar process can also be observed in the kidneys in the case of the formation of cystic cavities in them from urinary tubules that are for some reason devoid of connection with the rest of the urinary system.