[493] CD34 Staining in Neurofibromas: A Diagnostic Pitfall
JM Uchin, BP Rubin, JR Goldblum, SD Billings. Cleveland Clinic, Cleveland, OH
Background: Neurofibromas are benign neoplasms that have three well-documented growth patterns: localized, diffuse, and plexiform. We have reviewed many outside consultation cases in which neurofibromas were misdiagnosed as dermatofibrosarcoma protuberans (DFSP). Almost uniformly, the misdiagnosis was caused by misinterpretation of positive CD34 staining. Herein we describe the CD34 staining patterns of 44 excised neurofibromas.
Design: 16 cases of localized neurofibromas, 10 cases of plexiform neurofibromas, and 18 cases of diffuse neurofibromas were retrieved from archives. H&E slides were reviewed by 3 soft tissue pathologists and their diagnoses confirmed. Immunohistochemistry for CD34 (QBEnd/10, Ventana Medical Systems) using DAB. Cases were scored according to a semi-quantitative scale: 0 (negative staining), 1+ (< 25% staining), 2+ (25-50% staining), 3+ (> 50% staining).
Results: The IHC staining results are summarized in the table below. Localized neurofibromas ubiquitously demonstrate staining with CD34, in a predominantly widespread pattern. While diffuse and plexiform neurofibromas showed more variation in their CD34 staining patterns, ranging from widespread to focal to patchy, 96% of these subtypes expressed CD34.
CD34 Staining Results| Score | Localized NF | Plexiform NF | Diffuse NF |
|---|
| 0 | 0 | 0 | 1 | | 1+ | 0 | 3 | 4 | | 2+ | 1 | 0 | 3 | | 3+ | 15 | 7 | 10 | | Overall (+) | 16/16 (100%) | 10/10 (100%) | 17/18 (94%) |
Conclusions: Significant histological and immunohistochemical overlap can exist between neurofibroma and DFSP. In DFSP, immunoreactivity for CD34 can be crucial in establishing the diagnosis in small biopsies or challenging morphologic variants (e.g. myxoid DFSP). Our data demonstrate significant, often diffuse CD34 expression in all subtypes of neurofibroma. Awareness of this potential diagnostic pitfall can prevent misdiagnosis. This is especially true in the setting of diffuse neurofibroma- which shows significant histiologic overlap with myxoid DFSP, and with small biopsies of solitary neurofibroma. In addition, our data show that CD34 can be used as an additional reliable diagnostic marker for all morphologic variants of neurofibroma.
Category: Dermatopathology
Tuesday, March 10, 2009 1:00 PM
Poster Session IV # 69, Tuesday Afternoon
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