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Immunohistochemistry of p16 in nevi of pregnancy and nevoid melanomas: a clinical follow-up study
  1. Stephen S Koh1,2,
  2. Sean K Lau1,2,
  3. Brian F Roehmholdt1,3,
  4. David S Cassarino1,4
  1. 1 Kaiser Foundation Hospitals, Pasadena, California, USA
  2. 2 Department of Pathology and Dermatopathology, Kaiser Permanente Anaheim/Irvine Medical Center, Anaheim, California, USA
  3. 3 Department of Pathology and Dermatopathology, Kaiser Permanente Fontana/Ontario Medical Center, Fontana, California, USA
  4. 4 Department of Pathology and Dermatopathology, Kaiser Permanente Los Angeles Medical Center, Los Angeles, California, USA
  1. Correspondence to Dr Stephen S Koh, Department of Pathology and Dermatopathology, Kaiser Permanente Orange County - Anaheim/Irvine Medical Center, Anaheim, CA 92806, USA; stephen.s.koh{at}

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Immunohistochemistry (IHC) for p16 has been evaluated in melanocytic lesions,with most nevi exhibiting positivity for p16 while melanomas are more likely to show loss of p16 expression.1 This difference in expression has led to the use of p16 immunohistochemistry as a diagnostic marker for the distinction of nevi from melanoma.2

In a prior study, we analysed p16 expression in nevi of pregnancy, with particular emphasis on evaluating the potential utility of p16 as marker to distinguish these lesions from nevoid melanomas. The majority of nevi from pregnant patients demonstrated significant p16 positive immunohistochemical staining, while most nevoid melanomas showed significant loss of p16 expression.3 Since nevi from pregnant patients may display unusual morphological features4 that could potentially lead to a misdiagnosis, in particular nevoid melanoma, the results of our investigation supported use of p16 as an adjunctive diagnostic tool to distinguish between these lesions. One limitation of the prior study was lack of long-term clinical outcome data. Herein, we present clinical follow-up analysis exploring the relationship between p16 expression and clinical outcome in patients with nevi of pregnancy and nevoid melanoma.


Cases, as previously reported, consisted of 14 nevi and 20 patients with melanoma. Clinical follow-up data of the patients were obtained through our electronic medical record system. Recurrence or metastasis, number of months of follow-up, living or deceased status, chemotherapy treatment, and other pertinent information were …

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  • Handling editor Runjan Chetty.

  • Contributors SSK, SKL and BFR: substantial contributions to the conception or design of the work, or the acquisition, analysis or interpretation of data. SSK, SKL and DSC: drafting the work or revising it critically for important intellectual content. SSK and DSC: final approval of the version published. All authors: agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Disclaimer The opinions or assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of Southern California Permanente Medical Group.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.