THE PATHOLOGICAL ANATOMY 295 



Cysts, Some observers use the term a cyst" to include enlarged 

 colloid filled alveoli and designate such goiters as "cystic goiter." This 

 is wrong. First, because cyst formation is not a part of goiter forma- 

 tion, and secondly, there is no difference between the alveoli of normal 

 glands and of colloid goiters, except size. True thyroid cysts are common 

 for the reason that hemorrhage is common. Beck, Bloodgood (a), Roki- 

 tansky (a) (&). 



Two essential types of thyroid cysts may be differentiated. 



Cysts from hemorrhage into alveoli. 



Cysts from adenomas. 



Cysts due to hemorrhage into the alveoli are the usual thyroid 

 cysts. They vary in size from a few millimeters to six to eight centi- 

 meters in diameter. The smaller ones have the slightly thickened 

 alveolar walls as their cyst walls, while the larger cysts include in addi- 

 tion portions of the gland capsule or trabeculse together with whatever 

 new formation of connective tissue may have taken place. Calcifica- 

 tion of the cyst wall is quite frequently observed. The cyst contents 

 consist of blood in various stages of decomposition mixed with more 

 or less colloid, sometimes it is brown, pasty, sometimes viscid, sometimes 

 serous. In color the contents vary from dark-brown to clear amber- 

 yellow. Cholesterol is frequently present in these cysts. Bradley. 



Cysts arising from adenomas make up the majority of so-called 

 surgical cysts. ' The primary change in the adenoma leading to cyst 

 formation is probably an interference with the nutrition of the interior 

 of the tumor due to outgrowing its blood supply which is entirely 

 capsular, resulting in central necrosis. Hemorrhage then takes place and 

 the softening may extend to the capsule. More often there is a zone 

 of active adenoma tissue beneath the capsule varying from a few milli- 

 meters to a few centimeters in thickness. The original capsule of the ade- 

 noma forms the cyst wall. Acute, large hemorrhages may occur in cystic 

 adenomas. Also they form excellent sites for the lodgment and develop- 

 ment of pyogenic organisms, hence secondary abscess formation is relatively 

 frequent. Cysts of adenoma origin make up the largest cysts seen in 

 the thyroid. The contents of these cysts are, as a rule, more fluid than the 

 primarily hemorrhagic cyst. The material is frequently brownish in color 

 and may contain cholesterol and small masses or clumps of tissue debris. 

 In long standing cysts of this origin, a clear yellow or greenish fluid is not 

 uncommon. Clark and Farmer, Schneider, Tillaux. 



Developmental Defects and Anomalies 



The thyroid gland arises from a single ventral, midline "anlage" of 

 endoderm in the floor of the primitive pharynx, grows down or is dragged 

 down as the thyroglossal tract with the trachea and branches into right 



