LEPIDIC AND HYLIC TUMOURS 315 



Lepidomata, originating from the above lining membrane 

 tissues, and the Hylomata, originating and derived from tissues 

 developed from the embryonic pulp. 



I. Lepidomata or " Rind " Tumours 



A. Primary Lepidomata 



1. Bpilepidomata. 



Tumours whose characteristic constituents are overgrowths of 

 tissues, derived directly from the epiblastic lining membranes, 

 or true epiblast. 



(a) Typical. — Papilloma, epidermal adenomata (of sweat, 



salivary, sebaceous, and mammary glands, etc.). 

 (6) Atypical. — Epithelioma proper (of skin), carcinoma of 

 glands of epiblastic origin. 



2. Hypolepidomata. 



(a) Typical. — Adenoma and papilloma of digestive and 

 respiratory tracts, thyroid, pancreas, liver, bladder, 

 etc. 



(&) Atypical. — Carcinoma developing in the same organs 

 and regions. 



B. Secondary Lepidomata 



3. Mesolepidomata. 



Tumours whose characteristic constituents are cells derived in 

 direct descent from the persistent mesothelium of the embryo. 

 (a) Typical. — Adenoma of kidney, testicle, ovary, uro- 

 genital ducts ; adenoma of uterus and prostate ; 

 adenomas originating from the serous membranes, 

 " mesothelioma " of pleurae, peritoneum, etc. 

 (&) Atypical. — Cancer of the above-mentioned organs ; 

 squamous endothelioma, so called, of serous sur- 

 faces, epithelioma of vagina. 



4. Endothelial Lepidomata. 



Tumours originating from the endothelium of the blood and 

 lymph vessels ; endothelioma, perithelioma. 



II. Hylomata or " Pulp " Tumours 



1. Epihylomata. 



Tumours whose characteristic constituents are overgrowths of 

 tissues derived from the embryonic pulp of epiblastic origin. 



(a) Typical. — True neuroma, glioma. 



(b) Atypical. — " Gliosarcoma." 



