title: Hobnail hemangiomas (targetoid hemosiderotic hemangiomas) are true lymphangiomas.
abstract: BACKGROUND
  Hobnail hemangioma (targetoid hemosiderotic hemangioma) is a small benign vascular tumor of the superficial and mid-dermis. In contrast to its well-characterized histology, it has been unclear whether this tumor arises from blood vessel endothelial cells (BECs) or lymphatic vessel endothelial cells (LECs).
  
  
  METHODS
  We analyzed 10 hobnail hemangiomas by immunohistochemistry, using the recently described lymphatic endothelial cell marker, D2-40. For comparison, CD31, CD34, and alpha-smooth muscle actin expression were studied in consecutive sections of the paraffin-embedded tissues.
  
  
  RESULTS
  In all analyzed vessels, D2-40 labeled exclusively LECs, whereas BECs were consistently negative. In contrast to capillary BECs, either neighboring the tumors or intermingled, neoplastic endothelial cells of all 10 hobnail hemangiomas were strongly labeled by D2-40.
  
  
  CONCLUSIONS
  The results suggest a lymphatic origin for hobnail hemangiomas. This view is further supported by the CD34 negativity of endothelial cells and the lack of actin-labeled pericytes in hobnail hemangiomas, both characteristic of lymphatic vessels. Moreover, our analysis revealed that microshunts between neoplastic lymphatic vascular channels and small blood vessels occur, explaining some features of hobnail hemangiomas, such as aneurysmatic microstructures, erythrocytes within and beneath neoplastic vascular spaces, inflammatory changes, scarring, and interstitial hemosiderin deposits.
authors.affiliation: Department of Pathology, Justus-Liebig University of Giessen, Langhanstrasse 10, D-35392 Giessen, Germany. folker.e.franke@patho.med.uni-giessen.de
authors.forename: Folker E
authors.initials: FE
authors.lastname: Franke
authors.forename: Klaus
authors.initials: K
authors.lastname: Steger
authors.forename: Alexander
authors.initials: A
authors.lastname: Marks
authors.forename: Heinz
authors.initials: H
authors.lastname: Kutzner
authors.forename: Thomas
authors.initials: T
authors.lastname: Mentzel
mesh_terms: D000199:Actins / Q000378:metabolism; D000911:Antibodies, Monoclonal; D018952:Antigens, CD34 / Q000378:metabolism; D015415:Biomarkers / Q000032:analysis; D042783:Endothelial Cells / Q000378:metabolism; D006391:Hemangioma / Q000378:metabolism* / Q000473:pathology*; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D008202:Lymphangioma / Q000378:metabolism* / Q000473:pathology*; D009130:Muscle, Smooth / Q000378:metabolism; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000378:metabolism; D012878:Skin Neoplasms / Q000378:metabolism* / Q000473:pathology*
chemical_list: D000199:Actins; D000911:Antibodies, Monoclonal; D018952:Antigens, CD34; D015415:Biomarkers; D019408:Platelet Endothelial Cell Adhesion Molecule-1