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Peer-reviewedCC BY-NC-ND 4.0Journal of Cutaneous Pathology

Diagnostic Utility of PRAME Immunohistochemistry for Distinguishing Acral Melanoma From Acral Melanocytic Nevi

  • Kritsada Phatcharamaneepakorn1
  • Panitta Sitthinamsuwan1
  • Penvadee Pattanaprichakul2
  • Manasmon Chairatchaneeboon2
  • Nutcha Yodrabum3
  1. 1Department of Pathology, Faculty of Medicine Siriraj Hospital Mahidol University Bangkok Thailand
  2. 2Department of Dermatology, Faculty of Medicine Siriraj Hospital Mahidol University Bangkok Thailand
  3. 3Division of Plastic Surgery, Department of Surgery, Faculty of Medicine Siriraj Hospital Mahidol University Bangkok Thailand
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Abstract

Introduction: Preferentially expressed antigen in melanoma (PRAME) immunohistochemistry helps distinguish non‐acral melanocytic lesions, but few studies have addressed its value in acral lesions. We aimed to identify an optimal PRAME cut‐off score to differentiate acral melanoma (AM) from acral melanocytic nevi (AMN).

Methods: Formalin‐fixed, paraffin‐embedded specimens of AM, AMN, and small biopsy of atypical melanocytic lesions (AMLs) were included. PRAME staining was performed. Expression was categorized into five groups: 0 (0%), 1+ (1%–25%), 2+ (26%–50%), 3+ (51%–75%), and 4+ (> 75%). PRAME nuclear expression was compared between AM and AMN to identify the best cut‐off score, which was then assessed in small‐sized biopsies of AML specimens.

Results: We analyzed 62 AMs, 62 AMNs, and 23 AMLs. A PRAME score of ≥ 3+ optimally differentiated AM from AMN (sensitivity 80.6%, specificity 98.4%, positive predictive value 98%, and negative predictive value 83.6%). PRAME expression score ≥ 3+ was strongly associated with AM, whereas AMN showed expression score < 3+ (p < 0.001). However, one AM was completely negative for PRAME, and one AMN exhibited strong PRAME staining.

Conclusions: PRAME immunohistochemistry with a cut‐off of ≥ 3+ is useful for differentiating AM from AMN. However, false positivity and negativity of PRAME expression must be considered.

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Cite

BibTeXRIS
BibTeX
@article{phatcharamaneepakorn2026diagnostic,
  title = {{Diagnostic Utility of PRAME Immunohistochemistry for Distinguishing Acral Melanoma From Acral Melanocytic Nevi}},
  author = {Kritsada Phatcharamaneepakorn and Panitta Sitthinamsuwan and Penvadee Pattanaprichakul and Manasmon Chairatchaneeboon and Nutcha Yodrabum},
  journal = {Journal of Cutaneous Pathology},
  year = {2026},
  month = jun,
  doi = {10.1111/cup.70163},
  url = {https://doi.org/10.1111/cup.70163},
  note = {CC BY-NC-ND 4.0},
}
RIS
TY  - JOUR
TI  - Diagnostic Utility of PRAME Immunohistochemistry for Distinguishing Acral Melanoma From Acral Melanocytic Nevi
AU  - Kritsada Phatcharamaneepakorn
AU  - Panitta Sitthinamsuwan
AU  - Penvadee Pattanaprichakul
AU  - Manasmon Chairatchaneeboon
AU  - Nutcha Yodrabum
PY  - 2026
DA  - 2026/06/17
JO  - Journal of Cutaneous Pathology
DO  - 10.1111/cup.70163
UR  - https://doi.org/10.1111/cup.70163
AB  - Introduction: Preferentially expressed antigen in melanoma (PRAME) immunohistochemistry helps distinguish non‐acral melanocytic lesions, but few studies have addressed its value in acral lesions. We aimed to identify an optimal PRAME cut‐off score to differentiate acral melanoma (AM) from acral melanocytic nevi (AMN).  Methods: Formalin‐fixed, paraffin‐embedded specimens of AM, AMN, and small biopsy of atypical melanocytic lesions (AMLs) were included. PRAME staining was performed. Expression was categorized into five groups: 0 (0%), 1+ (1%–25%), 2+ (26%–50%), 3+ (51%–75%), and 4+ (> 75%). PRAME nuclear expression was compared between AM and AMN to identify the best cut‐off score, which was then assessed in small‐sized biopsies of AML specimens.  Results: We analyzed 62 AMs, 62 AMNs, and 23 AMLs. A PRAME score of ≥ 3+ optimally differentiated AM from AMN (sensitivity 80.6%, specificity 98.4%, positive predictive value 98%, and negative predictive value 83.6%). PRAME expression score ≥ 3+ was strongly associated with AM, whereas AMN showed expression score < 3+ (p < 0.001). However, one AM was completely negative for PRAME, and one AMN exhibited strong PRAME staining.  Conclusions: PRAME immunohistochemistry with a cut‐off of ≥ 3+ is useful for differentiating AM from AMN. However, false positivity and negativity of PRAME expression must be considered.
SN  - 0303-6987
SN  - 1600-0560
ER  -