TUMORS 155 



TERATOMA AND TERATOID TUMORS 



These are tumors composed of all three layers of the 

 embryo hypoblast, mesoblast, and epiblast. 



These tumors, may, in general, be looked upon as 

 arising from misplaced fetal remnants. 



Dermoid Cyst. This is a benign tumor, though some- 

 times prone to carcinomatous degeneration. It is com- 

 posed of a connective-tissue membrane lined with skin. 

 Its contents are the various appendages of the skin, 

 such as hairs, sebaceous glands, and occasionally teeth. 

 They grow very slowly and may remain latent, varying 

 in size from that of a pea to enormous masses. They 

 are found most frequently in the ovaries, less frequently 

 in the testicles, peritoneum, membranes of the brain, in 

 the neck, floor of the mouth, and about the eye.- 



Bigeminal Teratoma. In this form of tumor we have 

 the implantation of an ovum or fetus upon or within 

 the tissues of another fetus. The misplaced organism 

 may remain dormant, while the one upon which it is 

 implanted develops slightly or to considerable extent, 

 giving rise to various monsters. Where the extra 

 fetus is enclosed within another, it is termed endogenous 

 teratoma; where two are fused, one developing only in 

 part, it is called ectogenous teratoma. 



