Microphthalmia transcription factor immunohistochemistry for FNA biopsy of ocular malignant melanoma.

BACKGROUNDMicrophthalmia transcription factor (MiTF) is a sensitive and specific immunohistochemistry (IHC) marker for malignant melanoma (MM) in surgical resections, but its utility in cytology specimens has not been extensively studied. METHODSA search of the pathology database identified fine-needle aspiration biopsies signed out as MM or suspicious for MM (1998-2012). The final diagnosis and the IHC results were recorded, and all slides were re-reviewed. MiTF IHC (C5/D5 cocktail) was performed on alcohol-fixed, Papanicolaou-stained direct smears. Any amount of nuclear staining was considered positive. Staining was scored on a scale of 1 to 4 (1, 1%-24%; 2, 25%-49%; 3, 50%-74%; 4, 75%-100%). RESULTSTwo hundred seventy-four cases were diagnosed as MM, and 24 were diagnosed as suspicious for MM. IHC staining was performed for 25% (69 of 274) of the MM cases and for 33% (8 of 24) of the cases suspicious for MM. MiTF IHC of Papanicolaou slides was performed for 37% (101 of 274) of the MM cases (positive, 82% [83 of 101]; negative, 4% [4 of 101]; noncontributory, 14% [14 of 101]) and for 33% (8 of 24) of the cases suspicious for MM (positive, 38% [3 of 8]; noncontributory, 62% [5 of 8]). The majority of positive staining was scored as 3 or 4. The sensitivity of MiTF on Papanicolaou-stained slides was 95%. CONCLUSIONSMiTF is a useful IHC stain for the evaluation of ocular MM, and it is effective when it is performed on alcohol-fixed, Papanicolaou-stained aspirate smears. Cancer (Cancer Cytopathol) 2015;123:394-400. (c) 2015 American Cancer Society. This study is an evaluation of immunohistochemistry in the workup of fine-needle aspiration biopsies of ocular malignant melanoma and especially the new marker microphthalmia transcription factor. In addition, we show that microphthalmia transcription factor immunohistochemistry may be reliably performed on alcohol-fixed, Papanicolaou-stained direct smears.