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Dermatopathology: Practical & Conceptual April - June 1995
Searching for Diogenes: Bulge-Activation Hypothesis Part II—The Bulge is Not a Bulge
Cosimo Misciali, MD
A. Bernard Ackerman, MD
1927 Felix Pinkus
1951 Hermann Pinkus
1958 Hermann Pinkus
1961 Sanderson & Thiede
1987 Headington & Astle
1990 Leshin & White
1990 Cotsarelis, Sun, Lavker
1991 Sun, Cotsarelis, Lavker
1991 Lavker, Cotsarelis, Wei, Sun
1991 Lane, Wilson, Hughes, Leigh
1992 Jaworsky, Kligman, Murphy
1993 Yang, Lavker, Sun
1993 Lavker, Miller, Wilson, Costarelis, Wei, Yang, Sun
1993 Kobayashi, Rochat, Barrandon
1994 Rochat, Kobayashi, Barrandon
Normal structure of skin. In: Mehregan AH (ed). Pinkus" Guide to Dermatohistopathology. 4th ed. Norwalk, CT: Appleton-Century-Crofts 1986:5-39 (
Fig. 14 [Fig. 2-29] Bulge area of a small follicle. Bulge proliferation forms an epithelial tendon for strong arrector muscle (m). Elastic fibers surround follicular isthmus and upper part of bulge and fade out below it. Inner root sheath is dark (blue). O&G. (Reproduced with permission.)
"The bulge" denotes the lower end of a permanent follicle. Proliferations of "the bulge" that serve as attachment sites for the hair arrector muscle are similar structurally to trichoepitheliomas.
"The bulge," as a consequence of keratinization centrally, may give rise to milia.
Mehregan, like H. Pinkus, mentioned the similarity between bulges and trichoepitheliomas, but unlike Pinkus he avoided any reference to the proposition that trichoepitheliomas may be derived from "the bulge."
The "milia" of Mehregan are the "bubbles" of Zimmermann, and neither are true milia because they are lined by epithelium of the isthmus or of the stem, in contrast to authentic milia that are enveloped by epithelium of the infundibulum. The identity of these rarely encountered cystic structures that emanate from terminal follicles is not known. They do not seem to be true bulges.
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