Differentiating Neurotized Melanocytic Nevi From Neurofibromas Using Melan-A (MART-1) Immunohistochemical Stain

Department of Pathology and Immunology, Washington University School of Medicine, St Louis, Missouri, USA.
Archives of pathology & laboratory medicine (Impact Factor: 2.84). 07/2012; 136(7):810-5. DOI: 10.5858/arpa.2011-0335-OA
Source: PubMed


Neurotized melanocytic nevi and neurofibromas are common, benign cutaneous neoplasms. Usually they are histologically distinct from each other; however, neurotized melanocytic nevi and neurofibromas can be clinically and histologically similar.
To determine whether Melan-A (MART-1) immunohistochemical stain is sufficient to differentiate neurotized melanocytic nevi from neurofibromas.
Forty-nine consecutive specimens of melanocytic nevi with neurotization and 49 specimens of neurofibromas were selected. We used antibodies against Melan-A, S100, and neurofilament protein.
All of the melanocytic nevi showed Melan-A staining within the neurotized areas, with most of the areas staining strongly positive, whereas all the neurofibromas were completely absent of Melan-A stain. All of the nevi, including the neurotized areas, stained strongly and diffusely for S100, whereas all the neurofibromas showed a distinctive, sharp, wavy pattern of S100 staining. Neurofilament protein showed scattered staining of both melanocytic nevi and neurofibromas.
Our data indicate that Melan-A immunohistochemical staining is helpful in differentiating neurotized melanocytic nevi from neurofibromas when distinction on histomorphology alone is difficult.

25 Reads
  • [Show abstract] [Hide abstract]
    ABSTRACT: Whereas the pigmented (melanotic) variant of diffuse neurofibroma (DNF) with positivity for melanocytic markers is well recognized, expression of melanocytic markers in nonpigmented DNF has not been systematically studied. We analyzed 28 unselected consecutive DNFs for expression of melanocytic markers, including melan A, microphthalmia transcription factor (MITF), and HMB-45 antigen. For comparison, we also analyzed 40 localized skin neurofibromas and 7 intraneural neurofibromas. One case of nonpigmented DNF was analyzed by electron microscopy. Of the 28 DNFs studied by immunohistochemistry, 3 were pigmented and 25 nonpigmented. The 3 pigmented DNFs and 9 of 25 (36%) nonpigmented DNFs expressed melan A, MITF, and HMB-45 antigen. These markers were expressed either focally or more diffusely, typically in a minority of the lesional cells, and usually both in the dermal and subcutaneous portion of the DNF. Melan A was expressed in the largest number of the lesional cells (up to 50%), whereas only a small fraction of the melan A-positive cells (from 5% to 10% in most cases) also expressed HMB-45 antigen. None of the 47 non-DNFs expressed these markers. Ultrastructurally, melanosomes were present in some cells in nonpigmented DNF that expressed the melanocytic markers. Twenty-three of 28 (82%) DNFs, including 10 of 12 (83%) DNFs with melanocytic differentiation, were associated with neurofibromatosis type 1. Expression of melanocytic markers, including melan A, HMB-45 antigen, and MITF in DNF is a potential pitfall in differential diagnosis with melanocytic lesions that may clinically or histopathologically resemble DNF, in particular congenital melanocytic nevus with neurotization and neurofibroma-like melanoma.
    The American journal of surgical pathology 05/2013; 37(8). DOI:10.1097/PAS.0b013e31828950a3 · 5.15 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Tumors expressing both melanocytic and neural features can pose a diagnostic challenge to the dermatopathologist and provoke questions regarding lineage. We report a case of a tumor arising on the right cheek of a nine-year-old boy with neurofibromatosis type 1. This neoplasm featured nests of non-pigmented epithelioid cells arising within a neurofibroma. The entire tumor stained strongly with S100, while the epithelioid population stained with MART-1, HMB-45, and MiTF. The neoplasm demonstrates only scattered Ki-67 positivity. This tumor represents a neurofibroma with portions that have undergone melanocytic differentiation (melanocytic neurofibroma). This exceedingly rare tumor represents a distinct entity from neurotized melanocytic nevi, combined melanocytic nevi, or pigmented neurofibromas and provides further evidence that melanocytes arise indirectly from ventromedial neural crest-derived Schwann cell precursors.
    Journal of Cutaneous Pathology 01/2014; 41(5). DOI:10.1111/cup.12297 · 1.58 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Aim (1) A pilot study to determine the accuracy of interpretation of whole slide digital images in a broad range of general histopathology cases of graded complexity. (2) To survey the participating histopathologists with regard to acceptability of digital pathology. Materials and methods Glass slides of 100 biopsies and minor resections were digitally scanned in their entirety, producing digital slides. These cases had been diagnosed by light microscopy at least 1 year previously and were subsequently reassessed by the original reporting pathologist (who was blinded to their original diagnosis) using digital pathology. The digital pathology-based diagnosis was compared with the original glass slide diagnosis and classified as concordant, slightly discordant (without clinical consequence) or discordant. The participants were surveyed at the end of the study. Results There was concordance between the original light microscopy diagnosis and digital pathology-based diagnosis in 95 of the 100 cases while the remaining 5 cases showed only slight discordance (with no clinical consequence). None of the cases were categorised as discordant. Participants had mixed experiences using digital pathology technology. Conclusions In the broad range of cases we examined, digital pathology is a safe and viable method of making a primary histopathological diagnosis.
    Journal of Clinical Pathology 09/2014; 67(12). DOI:10.1136/jclinpath-2014-202491 · 2.92 Impact Factor
Show more