Original StudyThe “Intraepidermal Epithelioma” Revisited: Immunohistochemical Study of the Borst–Jadassohn PhenomenonLora, Viviana MD; Chouvet, Brigitte MD; Kanitakis, Jean MDAuthor Information From the Laboratory of Dermatopathology, Ed. Herriot Hospital, Lyon, France. Reprints: Jean Kanitakis, MD, Department of Dermatology, Ed. Herriot Hospital Group (Pav. R), 69437 Lyon cedex 03 France (e-mail: [email protected]). The American Journal of Dermatopathology: July 2011 - Volume 33 - Issue 5 - p 492-497 doi: 10.1097/DAD.0b013e3181fe6f90 Buy Metrics Abstract The true nature of the so-called intraepidermal epithelioma of Borst-Jadassohn is poorly understood; whether this represents a distinct tumor or a morphological phenomenon [Borst-Jadassohn phenomenon (BJP)] shared by different entities has been debated. So far, no detailed immunohistochemical studies have been performed to address this issue. The aim of our study was to get further insight into the pathogenesis of the intraepidermal epithelioma of Borst-Jadassohn/BJP. Tumors showing the BJP [mainly clonal seborrheic keratoses (cSK) and clonal Bowen disease (cBD)] were studied and compared with typical (nonclonal) counterparts. Cell nests in cSK, cBD, hidroacanthoma simplex (HS), and porocarcinoma (PC) showed strong expression of epidermal growth factor-receptors (EGF-R), Ki-67, p63, and p53. Cell nests of clonal SK and HS (but not of clonal BD or PC) expressed keratin 5/6. The expression of E-cadherin and the number of CD1a+ Langerhans cells were reduced within the nests of all lesions, whereas melanocytes were increased in all of them. Keratins 7 and 19 were not expressed in any of the lesions. Tumors showing the BJP exhibit some immunohistochemical differences, suggesting that they represent separate entities. However, they all show strong expression of EGF-R within intraepidermal keratinocyte nests, suggesting that the epithelial growth factor pathway plays a role in the development of the BJP. © 2011 by Lippincott Williams & Wilkins.