Controversies in DermatopathologyFibroepithelioma of Pinkus Is a Fenestrated TrichoblastomaBowen, Anneli R MD; LeBoit, Philip E MDAuthor Information From the Departments of Pathology and Dermatology, University of California, San Francisco, California. This work was supported in part by the Women’s Dermatologic Society Mentorship Program. Institutional review board approval was obtained for this study (#H25054-21310-01). Reprints: Philip E. LeBoit, Dermatopathology Section, University of California, San Francisco, 1701 Divisadero Street, Room 350, San Francisco, CA 94115 (e-mail: [email protected]). The American Journal of Dermatopathology: April 2005 - Volume 27 - Issue 2 - p 149-154 doi: 10.1097/01.dad.0000138051.71415.fe Buy SDC Metrics Abstract Pinkus described “pre-malignant fibroepithelioma” as a proliferation that gave rise to many tiny basal cell carcinomas within each lesion. Later authors have generally considered it to be an unusual variant of basal cell carcinoma (BCC). The delineation of trichoblastoma as the general term for the benign counterpart of BCC raises the possibility that the fibroepithelioma of Pinkus (FEP) would be better classified under that rubric. To address this subject, we examined the records of 114 patients with FEP for body site, age and sex distribution, and sections from 75 lesions. All FEP examined show a blunt interface with the underlying dermis (where one could be seen), differentiation toward follicular bulbs and papillae, and large areas of cellular stroma. FEP has a slight female preponderance in contrast to BCC, which is more common in males. Unlike the common types of BCC, FEP has an overwhelming predilection for the trunk and extremities, and only 5% of tumors are set in a dermis with significant amounts of solar elastosis. Next, FEP, BCC, and FEP with BCC-like areas were stained with MIB-1 (to assess proliferation), p53 (an oncogene product), and CK20 (a Merkel cell marker) antisera. FEP shows a low level of staining for p53 and MIB-1, in contrast to conventional BCCs that over-express these markers. FEP also shows retention of Merkel cells, a characteristic of benign neoplasms with follicular germinative differentiation but not in general of BCC. The BCC-like areas in some FEP tumors reflect these staining tendencies with less striking differences. Given the contrast between FEP and BCC with respect to site of occurrence, relationship to sun damage, histopathologic features, and immunohistochemical studies, it appears that FEP more closely resembles trichoblastoma than BCC. © 2005 Lippincott Williams & Wilkins, Inc.