[482] Expression of MiTF Can Distinguish Cellular Neurothekeoma from Plexiform Fibrohistiocytic Tumor.

Melanie D Fox, Steven D Billings, Jocelyn Moore, Antoinette B Thomas, Christopher R Shea, Thomas A Victor, Thomas L Cibull. NorthShore University HealthSystem, Evanston Hospital, IL; Cleveland Clinic, OH; University of Chicago, IL

Background: Overlapping histopathologic features of cellular neurothekeoma (CNT) and plexiform fibrohistiocytic tumor (PFHT) predominantly composed of histiocytic cells, make distinction between these entities challenging. Some have suggested that CNT and PFHT are related entities. No prior study has demonstrated a reliable immunohistochemical panel to differentiate these entities.
Design: Cases diagnosed as CNT and PFHT, from 2004-2010 were retrieved from the pathology departments of Evanston Hospital, Cleveland Clinic and The University of Chicago with accompanying pathology reports. Each case was reviewed by at least two dermatopathologists for confirmation of diagnosis. All cases were stained for PAX2, NKIC3, CD10 and MiTF.

Immunohistochemical expression of cellular neurothekeoma and plexiform fibrohistiocytic tumor
Age Sex Site Diagnosis PAX2 NKIC3 CD10 MiTF
74FLeft breastCNT3+3+3+3+
38MLeft thumbCNT-3+3+3+
12MRight hipCNT3+3+3+3+
10FLeft upper armCNT2+3+3+3+
31MRight scalpCNT3+3+3+3+
12MLeft shoulderCNT1+3+3+3+
22FRight flankCNT2+3+3+3+
UAUARight neckPFHT3+3+3+-
UAUALeft armPFHT-3+3+-
15MPosterior neckPFHT2+3+2+-
5MRight forearmPFHT2+3+2+-
48FLeft neckPFHT3+3+3+-
CNT = cellular neurothekeoma, PFHT = plexiform fibrohistiocytic tumor, 3+ > 75% positive expression; 2+ = 25-75% positive expression; 1+ < 25% positive expression; - = no expression; UA=unavailable

Conclusions: CNT and PFHT share many histopathologic features as well as IHC staining patterns. Of the stains we evaluated, we found that both CNT and PFHT were uniformly positive for NKIC3 and CD10 and both were frequently PAX2 positive. MiTF was strongly and diffusely positive in CNT and was consistently negative in the PFHT. Expression of MiTF may be a reliable marker for distinguishing CNT from PFHT predominantly composed of histiocytic cells.
Category: Dermatopathology

Monday, February 28, 2011 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 72, Monday Morning


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