THE PATHOLOGICAL ANATOMY 



273 



Fig. 8. Normal human thyroid 

 showing trabecula and its relation to 

 stroma. 



The microscopical appearance of the thyroid unit the alveolus, is simi- 

 lar in all animals from fish to man. The alveoli are in general round or 

 oval, closed spaces lined with a single layer of low cuboidal, or at 

 most cuboidal epithelium. (High cuboidal or columnar epithelium 

 always indicates hypertrophy.) The cells are quite regular in size, al- 

 though one can often distinguish the so-called chief and colloid cells. They 

 probably represent different stages of 

 secretory activity. The nuclei are 

 small, basal and vesicular. The colloid 

 lies in contact with the free border of 

 the epithelial cells and completely fills 

 the alveolus save for occasional vacuole- 

 like areas. It is homogeneous and stains 

 deeply with acid dyes. The colloid of 

 adjacent alveoli varies in consistency 

 and in staining intensity. The blood 

 and lymph capillaries form richly anas- 

 tomosing networks about each alveolus 

 and come into very close relation with 

 the lining epithelium. In the human 

 thyroid, particularly in early life, there 

 are groups of undeveloped thyroid cells 

 the so-called "thyroid rests" lying in the stroma between the developed 

 alveoli. There are normally lymphoid cells in the stroma and under 

 conditions of generalized lymphoid hyperplasia, as in myxedema, exoph- 

 thalmic goiter, Addison's disease and status lymphaticus these foci may 

 undergo marked hyperplasia. Anderson, Arnold, Bartels, R. R. Bensley 

 (a), Cavatorti, Cowdry, Flint, Forsyth (a), Francois-Frank and Hallion, 

 Kolliker, Langendorf, Lindemann, Major, Matsunaga, Norris (ft), Rhine- 

 hart, Schmidt, Simon, Stewart, Sfreiff. 



Hypertrophies and Hyperplasias 



This group comprises the developmental and growing stages of all 

 goiters irrespective of their clinical associations both in man and in the 

 lower animals, in simple goiter, in exophthalmic goiter and in myxedema 

 and cretinism. Hypertrophy and hyperplasia represent different de- 

 grees of the same process. They must be considered together, although 

 technically, hypertrophy may be said to end when cell proliferation begins. 

 The proper physiological and sequential relation of these changes is simple, 

 although in human goiter there are many secondary and complicating vari- 

 ations in morphology that have led to controversy and confusion. This 

 relationship of hyperplasias to the normal, atrophic and colloid thyroid is 

 shown in the following scheme: Marine and Lenhart (/) (#), Carlson, 

 Hesselberg, Pflug, Zielinska. (See Figs, 9 to 14.) 



