382 



HISTOLOGY OF THE MORBID PROCESSES. 



structure of each individual tumor must be carefully weighed before 

 a conclusion as to its benignancy or malignancy is reached. Aden- 

 omata are benign in proportion as they adhere to the structure of a 

 normal gland of the type which they simulate. They approach 



FIG. 348. 



Section of the mammary gland at the beginning of lactation ; more highly magnified. 



(Altmann.) 



malignancy when they become atypical and show a tendency to 

 infiltrate their surroundings. The adenomata of the rectum, 

 already referred to, are likely to prove malignant, and in their 

 structure they show a departure from the simple type of tubular 

 gland normally present in the rectum (Fig. 351). They also dis- 



FIG. 349. 



'Section of the mammary gland in a state of involution. (Altmann.) From a woman, aged 

 twenty-five, nine months after the cessation of functional activity. 



play a marked tendency to infiltrate their surroundings. While 

 they belong to a group of generally benign tumors, they possess 

 an atypical structure and a power of infiltration that reveal their 

 malignant character. 



2. Carcinoma. The epithelium of developing secreting glands 



