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PRAME expression in melanocytic proliferations with intermediate histopathologic or spitzoid features
Shyam S Raghavan1, Jennifer Y Wang2,3, Shirley Kwok2
1Department of Pathology, University of Virginia School of Medicine, Charlottesville, Virginia, USA.
Background:
PRAME (PReferentially expressed Antigen in MElanoma) has shown utility in distinguishing melanoma from benign melanocytic lesions, but knowledge of its expression pattern in intermediate melanocytic and spitzoid proliferations is limited.
Methods:
Immunohistochemical expression of PRAME was examined in 112 melanocytic proliferations with intermediate histopathologic or spitzoid features.
Results:
Any intensity of nuclear PRAME staining in at least 60% of lesional melanocytes was determined as the best threshold for diffuse staining in this cohort. Nearly all non-spitzoid melanomas (23/24; 95.8%) demonstrated diffuse PRAME expression. PRAME was completely negative in 95.6% (43/45) of mitotically-active nevi, traumatized nevi, nevi with persistent/recurrent features, and dysplastic nevi. Most Spitz nevi (15/20) and atypical Spitz tumors (10/13) entirely lacked PRAME expression. One Spitz nevus, one atypical Spitz tumor, and one spitzoid melanoma (1/2) demonstrated diffuse PRAME expression.
Conclusions:
Although diffuse PRAME expression is generally limited to malignant melanoma, benign Spitz nevi and atypical Spitz tumors can infrequently express diffuse PRAME. PRAME immunohistochemistry can be useful in the evaluation of atypical melanocytic proliferations with intermediate histopathologic features but should be interpreted with caution in the setting of spitzoid neoplasms.
Insights
PRAME expression helps differentiate melanoma from benign lesions. While usually absent in Spitz nevi and atypical Spitz tumors, rare cases can show PRAME, requiring careful interpretation.
Area of Science:
- Dermatopathology
- Oncology
- Immunohistochemistry
Background:
- PRAME (PReferentially expressed Antigen in MElanoma) is a marker for melanoma.
- Its expression in intermediate melanocytic and spitzoid lesions is not well-established.
Purpose of the Study:
- To evaluate PRAME expression in melanocytic proliferations with intermediate or spitzoid features.
- To determine the utility of PRAME immunohistochemistry in differentiating these lesions.
Main Methods:
- Immunohistochemical analysis of PRAME in 112 melanocytic proliferations.
- Defined diffuse PRAME expression as nuclear staining in ≥60% of lesional melanocytes.
Main Results:
- 95.8% of non-spitzoid melanomas showed diffuse PRAME expression.
- PRAME was negative in 95.6% of benign and dysplastic nevi.
- Most Spitz nevi and atypical Spitz tumors lacked PRAME, but rare cases showed expression.
Conclusions:
- Diffuse PRAME expression is predominantly seen in malignant melanoma.
- PRAME is a useful diagnostic aid for atypical melanocytic proliferations but requires cautious interpretation in spitzoid neoplasms due to infrequent expression.
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