PATHOLOGY OF PINEAL TUMOURS 43I 



do they occur near the midline. They are regularly connected with the 

 meninges. Bostroem concludes that all cholesteatomata arise from 

 embryonal epidermal inclusions. 



3. Teratomata. — These tumours arise exclusively in young males 

 from 4 to 16 years of age, and are associated with precocious sexual 

 development, hirsutes, and sometimes with adiposity and general over- 

 growth. 



These complex teratcmata are of moderate size ; they may be solid 

 or cystic, and are usually circumscribed. They give rise to marked pres- 

 sure signs. They may consist almost entirely of hair, sebaceous material, 

 epidermoid cysts, cartilage, calcific grains, fat tissue and non-medullated 

 nerve-fibres, and smooth muscle. l A small layer of normal pineal tissue 

 may be found beside and unusually compressed and displaced by the 

 tumour. They are firm in consistency, irregular and knobbly on the 

 surface, often with elongated shreds of tela choroidea adherent to the 

 upper and posterior surface. 



Their nature and origin is obscure, but of interest ; they are probably 

 derived from embryonic vestiges. The dermal structures, such as hair 

 and sebaceous glands, require an ectodermal tissue for their development, 

 which may possibly reach the pineal gland by the same developmental 

 disturbances that give rise to cholesteatomata. It must also be remembered 

 that in certain reptiles and fishes the pineal is a well-developed organ 

 which passes through a minute foramen in the skull and reaches the surface. 

 Alternatively these may develop by pseudogestation from a fertilized filial 

 polar body. 



4, 5. Pinealomata and Pineoblastomata. — Tumours arising from the 

 pineal gland tend to resemble the structure of the developing pineal at 

 some definite stage of its development. The more primitive the type 

 that is found in these tumours, the more rapidly growing and more 

 invasive is the growth. The primitive type of such tumours is termed 

 pineoblastoma. The course is usually short. If the tumour cells resemble 

 more the adult type of pineal structure, they are slow growing, less 

 invasive, are less liable to haemorrhage, and less vascular, and the tumour 

 is termed pinealoma. 



Pineoblastomata : these tumours are usually soft, with a tendency to 



1 Transversely striated muscle fibres have also been found in teratomata of the pineal 

 gland, and very occasionally in the normal gland, more especially in the ox, as described 

 by Nicolas and Dimitrowa (Fig. 284;. Striated muscles fibres have, moreover, been 

 observed by Hammer in the epiphysis of a human foetus aged 5 months, and cells which 

 have been described as "myoid" in the adult human organ. They have been found 

 chiefly in the vascular connective tissue septa or trabecular, and usually appear as isolated 

 fibres, as in the specimen described by Dimitrowa. In some cases the nucleus is central 

 and the general appearance of the fibres is intermediate between that of the striped and 

 unstriped types of muscle-fibres. 



