Abstract:

Context: Distinguishing between deep penetrating nevi (DPN), blue nevi (BN) and invasive malignant melanoma (IMM) can pose a diagnostic challenge primarily due to overlapping histology. A few studies have demonstrated utility of B-catenin in differentiating between deep penetrating nevi and other melanocytic lesions including invasive malignant melanoma. DPN is believed to arise as a result of joint activation of the MAP kinase pathway and dysregulation of the B-catenin pathway. B-catenin expression has also been described in a subset of malignant melanoma. Objective: To further explore the utility of B-catenin in distinguishing DPN and BN from IMM in our institution. Design: 30 cases corresponding to various melanocytic diagnoses (including DPN, BN, Cellular BN, compound melanocytic nevus with congenital features and IMM). Two of the authors (KK and AA) are reviewing the cases to verify diagnoses and see which IHC stains have been performed. Subsequently, we will perform additional immunohistochemical stains on tissue blocks with verified diagnoses to generate a complete set of cases with these IHC stains. Results and Conclusion: In our studies so far, we have found that B-catenin nuclear positivity is seen in definitive cases of DPN and that BN lacks B-catenin nuclear positivity. We have also seen cases where it is difficult to interpret the degree of positivity of the B-catenin stain. By analyzing the patterns of expression for these IHCs, we will endeavor to find thresholds of IHC expression that are valid for distinguishing DPN from BN and IMM.

Financial Disclosure:
No current or relevant financial relationships exist.

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Ayodele Adelanwa, MD