Atypical Cellular Unguioblastic Fibroma-A Rare Case With More Atypical Histological Features Than Previously ReportedPetersson, Fredrik MD, PhD; Tang, Aymeric Lim Yu MD; Jin, Andre Cheah Eu MD; Barr, Ronald J MD; Lee, Victor K MDAmerican Journal of Dermatopathology: June 2010 - Volume 32 - Issue 4 - pp 387-391 doi: 10.1097/DAD.0b013e3181c03402 Extraordinary Case Report Abstract Author Information We herein present the clinicopathological features of an atypical cellular unguioblastic fibroma, a rare onychomatrical tumor, in an adult woman of Southeast Asian origin. The tumor displayed both diffuse hypercellularity and atypia in the mesenchymal component and the presence of large multinucleated cells with a ring-/floret-like arrangement of irregular and hyperchromatic nuclei. The mesenchymal cells displayed a patchy weak positive immunereactivity for CD34 (including atypical and wreath-like multinucleated cells) and for CD10 but were negative for low molecular weight cytokeratins, epithelial membrane antigen, CD68, factor XIIIa, smooth muscle actin, desmin, and HMB-45. The proliferative index as measured immunohistochemically (Mib-1/Ki-67) was 5%. The extent of these atypical histological features has not previously been described. One-year follow-up has been uneventful. From the *Department of Pathology; †Department of Hand and Reconstructive Microsurgery, National University Health System, Singapore; and ‡Laguna Pathology Medical Group, Laguna Beach, CA. Reprints: Fredrik Petersson, MD, PhD, Department of Pathology, National University Health System, 5 Lower Kent Ridge Road, Singapore 119074 (e-mail: email@example.com). Copyright © 2010 Wolters Kluwer Health, Inc. All rights reserved.