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M.W. Dorey, S. Brownstein, H. Faraji, S. Robertson, R. Prokopetz, D.R. Jordan; Immunohistochemical Profile and Histochemical Analysis of Primary Acquired Melanosis of the Conjunctiva . Invest. Ophthalmol. Vis. Sci. 2003;44(13):2427.
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Purpose: To develop ancillary diagnostic tests to identify and confirm the presence and extent of atypia amongst the melanocytic lesions of primary acquired melanosis (PAM) of the conjunctiva. Methods: 10 specimens of PAM with atypia were obtained through the ocular pathology registry at the University of Ottawa Eye Institute from May 1994 to November 2002. Sections from each formalin-fixed paraffin-embedded specimen were stained with hematoxylin-eosin (including on bleached specimens) and periodic acid-Schiff (PAS) and immunostained with anti-S-100, HMB-45 (anti-gp100), melanoma cocktail (anti-melan-A and HMB-45), pan melanoma cocktail (anti-melan-A, HMB-45, and anti-tyrosinase), anti-melan-A, anti-Ki67 (MIB-1), anti-tyrosinase (T311), anti-microphthalmia-associated transcription factor (D5), and vimentin. These specimens were processed with the 3,3 diaminobenzidine (DAB) substrate and the Vector Red substrate methods. We similarly looked at PAM lesions without atypia, conjunctiva, as well as choroidal melanomas as controls. Results: The melanocytes were best demonstrated with the melanoma cocktail (anti-melan-A and HMB-45), pan melanoma cocktail (anti-melan-A, HMB-45, and anti-tyrosinase), anti-melan-A, and anti-tyrosinase (T311), all of which showed 100% positive staining. The melanocytes were often weakly stained by anti-MIB-1, anti-microphthalmia-associated transcription factor, and anti-S-100 and were negative in the atypical melanocytes in some of the cases. HMB-45 showed the highest specificity to atypical melanocytes (80%) but was less sensitive than the newer markers (80%). In the majority of cases, the DAB method could not differentiate between brown melanin pigment and brown pigmented immunostain in the atypical melanocytes, making it difficult to establish the presence and extent of atypia with these immunostains. The vector red method allowed easy differentiation amongst the melanin pigment from the red pigmented immunostain in the atypical melanocytes. Conclusions: The popular DAB method is often not useful in the identification of melanocytes in PAM and should be replaced by the vector red method. We believe our study is the first to demonstrate that HMB-45 is the only antibody with relatively high specificity to the atypical melanocytes of PAM. The results from this study may aid in making a more timely, definitive, and complete histopathological diagnosis of PAM with atypia.
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