31 January 2007 – Case of the Week #72


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We thank Dr. Adrian A. Suarez, National Children’s Hospital, San Jose, Costa Rica, for contributing this case.  We invite you to contribute a Case of the Week by sending an email to NPernick@PathologyOutlines.com with microscopic images (any size, we will shrink if necessary) in JPG or GIF format, a clinical history, your diagnosis and any other images (gross, immunostains, EM, etc.) that may be helpful or interesting.  We will write the discussion (unless you want to), list you as the contributor, and send you a check for $35 (US) for your time after we send out the case.  Please only send cases with a definitive diagnosis. 


Case of the Week #72


Clinical history


A two year old boy had a tender, palpable mass in his right parietal region (#1, #2).  Physical exam showed no skin lesions or enlarged organs, and there were no neurological abnormalities.  X-ray films and CT scans of his skull showed lytic masses involving both parietal bones and extending into adjacent soft tissues (Xray, CT scan).  The base of the skull was spared.  Blood chemistries were within reference values.


As is usual at our Institution, a fine needle aspiration biopsy was performed.

Smears were fixed in 95% ethanol and stained with Papanicolau (image1, image2).  They were highly cellular and showed a predominantly non-cohesive population of medium sized cells with mild pleomorphism.  Some cells were multinucleated.  Nuclei were round, oval or bean shaped with prominent longitudinal grooves.  Chromatin was fine and even.  A rare mitotic figure was seen. The background was clean and included only a rare eosinophil and no lymphoglandular bodies.  


What is your diagnosis? 


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Langerhans cell histiocytosis




The diagnosis was confirmed by a strongly positive CD1a stain (CD1a).


Langerhans cell histiocytosis, formerly called Histiocytosis X, is a neoplasm of Langerhans cells, which are antigen presenting cells.  It typically involves children or adolescents, and presents with solitary bone involvement (formerly called eosinophilic granuloma), multiple bone involvement or multiple organ involvement (see also our Bone chapter). 


Grossly, it is a sharply circumscribed mass, often involving the skull, jaw, humerus, ribs or femur.  Microscopically, there is infiltration by Langerhans cells, which may be accompanied by other inflammatory cells, fibrosis and necrosis.  Langerhans cells, by both H&E and cytology smears, are large polygonal cells with abundant eosinophilic cytoplasm.  They have distinctive oval nuclei with longitudinal grooves resembling coffee beans, and no prominent nucleoli.


Langerhans cells are immunoreactive for S100, CD1a, vimentin and Langerin, with variable CD68 staining.  They are negative for HAM56, CD21 and CD35.  Electron microscopy shows prominent electron dense cross striations, also called Birbeck granules.


CD1a is a T cell surface antigen important in dendritic cell presentation of glycolipids and lipopeptide antigens, and its presence is fairly specific for Langerhans cell histiocytosis.  However, it is also positive in T cell disorders, including cutaneous T cell lymphoma and T-ALL, as well as some other conditions (see CD1a in CD markers CD1 to CD49 chapter)


The differential diagnosis includes other histiocytic disorders, including sinus histiocytosis with massive lymphadenopathy, monocytic leukemia and mastocytosis.


Excision is usually curative for solitary lesions, but they may recur (“reactivate”) in up to 37% of cases with single system-multifocal disease, usually within 2 years (Pediatr Blood Cancer 2007 Jan 24; [Epub ahead of print])


References: eMedicine



Nat Pernick, M.D., President
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