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Int J Clin Exp Pathol. 2013 Jul 15;6(8):1658-64. Print 2013.

Micropthalmia transcription factor (MITF) as a diagnostic marker for metastatic melanomas negative for other melanoma markers.

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1
Department of Pathology, University of Oklahoma Health Sciences Center, Oklahoma city, Oklahoma 73104, USA.

Abstract

Metastatic malignant melanoma has a wide spectrum of histopathologic patterns and often lacks melanin pigment. Without a known primary tumor, the diagnosis of metastatic malignant melanoma relies on a combination of morphology and immunohistochemical profile. Infrequently, commonly used markers for melanoma (S100, HMB45, Melan-A and Tyrosinase A) are negative. These cases pose critical diagnostic challenges. Recent studies show that Microphthalmia Transcription Factor (MITF) has high sensitivity (88-100%) and specificity for metastatic melanoma. We are reporting here three cases of high grade tumors that were studied by a comprehensive immunohistochemical panel including cytokeratins, S100, HMB-45, Melan A, Tyrosinase, and MITF. All three tumors were also analyzed for the presence of BRAF mutations. All three metastatic tumors were negative for S100, Melan A, HMB-45 and Tyrosinase but positive for MITF. Subsequent to the diagnoses, previously existing or concurrent primary melanomas were identified in 2 of the 3 cases. Interestingly, S100, Melan A, and HMB-45 were positive in the primary tumors. No BRAF (V600E) mutations were identified in the three metastatic melanomas and CD 117 (c-kit) was positive in one of the cases. In summary, our experience shows that MITF can be a valuable adjunct in the diagnosis of metastatic tumors that are suspicious for melanoma but negative for other melanoma markers.

KEYWORDS:

Melanoma; Microphthalmia Transcription Factor; immunohistochemistry

PMID:
23923085
PMCID:
PMC3726983
[Indexed for MEDLINE]
Free PMC Article
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