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PRAME/MELAN-A double immunostaining as a diagnostic tool for conjunctival melanocytic lesions: A South American
Pedro Carvajal1, Pablo Zoroquiain1
1Pathology Department, School of Medicine, Pontificia Universidad Católica de Chile, Chile.
Introduction:
PRAME (PReferentially expressed Antigen in Melanoma) is an antigen that is predominantly expressed in human melanomas. In cutaneous melanocytic lesions, PRAME expression is associated with malignancy. The objective of this study was to evaluate the co-expression of PRAME and Melan A to evaluate their diagnostic value in different conjunctival melanocytic lesions (CML).
Methods:
37 CML (23 nevi, 9 primary acquired melanosis (PAM), and 5 conjunctival melanomas) were evaluated by immunohistochemistry for PRAME and Melan-A. The percentage of melanocytic cells co-expressing PRAME and Melan-A was qualitatively evaluated as follows: negative, 0%; 1 + , 1-25%; 2 + , 26-50%; 3 + , 51-75% and 4 + , ≥ 76%.
Results:
Of the invasive melanoma cases, 80% showed a 4 + pattern of marking, whereas 20% showed a 3 + pattern. 11% of the PAMs showed a 4 + pattern and 88.9% showed a 1 + pattern. All the nevi showed a 1 + pattern. The sensitivity and specificity of PRAME 4 + for differentiating high-grade CML from the benign and low-grade grouped CML are 93% and 100%, respectively.
Conclusion:
PRAME/MELAN-A double immunostain is particularly useful to differentiate benign from malignant conjunctival melanocytic lesions.
Insights
The PReferentially expressed Antigen in Melanoma (PRAME) and Melan-A double immunostain effectively distinguishes benign from malignant conjunctival melanocytic lesions. High PRAME expression (4+) showed 93% sensitivity and 100% specificity for malignancy.
Area of Science:
- Ophthalmology
- Dermatopathology
- Oncology
Background:
- PReferentially expressed Antigen in Melanoma (PRAME) is a marker predominantly found in melanomas and associated with malignancy in cutaneous lesions.
- Conjunctival melanocytic lesions (CML) require accurate differentiation between benign and malignant types for appropriate patient management.
Purpose of the Study:
- To evaluate the diagnostic utility of co-expressing PRAME and Melan-A in distinguishing various conjunctival melanocytic lesions.
- To assess the sensitivity and specificity of PRAME expression patterns in classifying CML.
Main Methods:
- Immunohistochemistry was performed on 37 conjunctival melanocytic lesions (23 nevi, 9 primary acquired melanosis, 5 melanomas) to detect PRAME and Melan-A.
- Melanocytic cell co-expression of PRAME and Melan-A was quantitatively assessed using a grading scale (0 to 4+).
Main Results:
- Malignant conjunctival melanomas showed high PRAME expression (4+ in 80%, 3+ in 20%).
- Primary acquired melanosis (PAM) cases exhibited variable PRAME expression (4+ in 11%, 1+ in 88.9%), while nevi consistently showed low expression (1+).
- A PRAME 4+ pattern demonstrated 93% sensitivity and 100% specificity for differentiating high-grade CML from benign and low-grade lesions.
Conclusions:
- The PRAME/Melan-A double immunostain is a valuable tool for differentiating benign from malignant conjunctival melanocytic lesions.
- High PRAME expression is a strong indicator of malignancy in conjunctival melanocytic lesions.
