17. Proliferating tricholemmal cyst

 
Quotation from the 9th edition of Lever's:
 
"There appears to be a spectrum of cases ranging from a proliferative trichilemmal cyst to a frankly malignant proliferating trichilemmal tumor. It has been proposed by some that proliferating trichilemmal cysts may be low-grade carcinomas."
 
Reference in the 9th edition to concepts contrary by A. Bernard Ackerman et al. (ABA): None.
 
Statements contrary by ABA:
 
"What has for decades been called "proliferating tricholemmal cyst" is not a cyst but a carcinoma that begins in a pre-existing follicular cyst. Both the cyst and the carcinoma that develops in it show differentiation toward the outer sheath at the isthmus (which, morphologically, is indistinguishable from the outer sheath as it involutes at a stage in catagen)."
 
Ackerman AB, Mones J. Proliferating tricholemmal cystic carcinoma (Revision of chapter XXV of the volume titled Neoplasms with Follicular Differentiation, 2nd edition by Ackerman, Reddy, and Soyer, Ardor Scribendi, Ltd., 2001. Dermatopathology Pratical & Conceptual 9(2), 2003.
 
Other works of ABA in which the ideas contrary are expressed:
 
Ackerman AB, Mones J. Resolving Quandaries in Dermatology, Pathology and Dermatopathology. pp 306-311. New York: Ardor Scribendi, 2001.