10 January 2008 – Case of the Week #107


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We thank Dr. Mowafak Hamodat, Eastern Health of Newfoundland and Labrador, St. John’s, Canada for contributing this case.  To contribute a Case of the Week, email NatPernick@Hotmail.com with the clinical history, your diagnosis and microscopic images in JPG, GIF or TIFF format (send as attachments, we will shrink if necessary).  Please include any other images (gross, immunostains, etc.) that may be helpful or interesting.  We will write the discussion (unless you want to), list you as the contributor, and send you $35 (US dollars) for your time after we send out the case.  Please only send cases with a definitive diagnosis, and preferably cases that are out of the ordinary.


Case of the Week #107


Clinical History


A 37 year old man had a skin lesion on the back, which was excised.


Micro images: #1;  #2;  #3#4#5

Immunostains: CD31 #1#2   


What is your diagnosis?




























Retiform hemangioendothelioma




Retiform hemangioendothelioma is a low grade variant of angiosarcoma that usually occurs in the distal extremities of young individuals.  Weiss and Goldblum use the term hobnail hemangioendothelioma for retiform and Dabska-type tumors, which they believe to be closely related (Weiss: Enzinger and Weiss's Soft Tissue Tumors, 2007 (5th Ed)).


Microscopically, the reticular dermis and subcutaneous tissue have a retiform (net-like, similar to rete testis) pattern of blood vessels that disperse through the tissue, and is highlighted by endothelial markers.  The vessels are lined by monomorphic hobnail endothelial cells with scant cytoplasm and rounded, naked-type nuclei.  There often is a prominent lymphocytic infiltrate, as seen focally in this case.  There are no epithelioid areas or cytoplasmic vacuoles (AJSP 1994;18:115).  They are rarely multiple (Am J Dermatopathol 1996;18:606)


The endothelial cells are immunoreactive for CD34 (strong), CD31 and vWF.  They are negative for keratin.


The differential diagnosis includes angiosarcoma, which may focally have low grade features, but also exhibits areas of marked atypia and pleomorphism.  Angiosarcomas also dissect between individual collagen bundles and have mitotic activity.  Hobnail hemangioma is a smaller, more superficial and more localized lesion, with papillary dermal vessels that disappear into the reticular dermis.


Treatment is wide local excision.  These tumors are considered to have intermediate malignancy, with frequent recurrence (particularly if a wide excision was not done), but only rare metastases, and no tumor related deaths.




Nat Pernick, M.D., President
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