CYTO-DIAGNOSIS 



259 



good sign, in that they do not indicate a tuberculous or septic 

 origin (Plate X., Fig. i). 



Pleuritic Exudates due to Malignant Disease.— The 

 appearances vary, and a definite diagnosis cannot always be 

 made. There is no criterion by which an isolated malignant cell 

 can be distinguished from an active endothelial cell. In some 

 cases, however, the masses of cells, which can be seen to be solid 

 and several cells thick* occur in the exudate mixed with red cor- 

 puscles and a few leucocytes. These cells are variable in size, 

 usually stain deeply, and often have a well-marked nucleolus. In 

 the figure shown (which comes from the ascitic fluid in a case 



Fig. 50. — Malignant Masses in Ascitic Fluid. 



of carcinoma of the ovary) the resemblance to an alveolus of 

 carcinoma as seen in a section is very distinct (Fig. 50). 



In other cases, and much more frequently, these masses are 

 absent, and their place is taken by large endothelial cells (often 

 many times larger than a red corpuscle), which can be seen in a 

 wet preparation to be in various stages of fatty and other forms 

 of degeneration, and which in dry preparations are found to be 

 extensively vacuolated (Plate X., Fig. 3), and often contain 

 ingested red corpuscles. These may be arranged in masses, are 

 mixed with red corpuscles, and perhaps a leucocyte or two. 



* As shown by focussing up and down whilst examining a wet specimen so 

 as to obtain a series of ' ' optical sections." 



