Reactive angioendotheliomatosis (RAE) is a rare cutaneous vascular disorder characterized by intravascular hyperplasia of endothelial cells, sometimes with a vascular proliferation. Intravascular histiocytosis (IH) is a similar vascular disorder characterized by the presence of dilated vessels containing aggregates of mononuclear histiocytes (macrophages) within their lumina. Although their pathogenesis remains uncertain, there has been speculation about the possible relationship between IH and RAE. We report a case of coexistence of RAE and IH in a patient who underwent a wide reexcision of a metastatic malignant melanoma. The excision specimen did not show any residual melanoma but exhibited an intravascular collection of CD-68–positive histiocytes admixed with CD-31–positive endothelial cells and fibrin surrounded by D2-40–positive vascular wall. The presence of intravascular cells initially raised concern of intravascular invasion by melanoma. As there was no clinical lesion and immunohistochemical stains for melanocytic makers were negative, we interpret this as an incidental finding. Knowledge of this benign vascular disorder is important because the histologic changes may be mistaken for intravascular invasion of a malignant neoplasm.
*Dermatopathology Section, Department of Dermatology, Boston University School of Medicine, Boston, MA; and
†Department of Pathology and Immunology, Baylor College of Medicine, Houston, TX. P. P. Aung is currently affiliated to the Department of Pathology and Lab Medicine, UT-MD Anderson Cancer Center, Houston, TX.
Reprints: Jag Bhawan, MD, Dermatopathology Section, Department of Dermatology, Boston University School of Medicine, 609 Albany St, J-309, Boston, MA 02118 (e-mail: email@example.com).
The authors declare no conflicts of interest.
P. P. Aung and L. Y. Ballester contributed equally.