Correlation of melanoma gene expression score with clinical outcomes on a series of melanocytic lesions.

A 23-gene expression signature was recently developed as an adjunct to histopathology to differentiate melanocytic nevi from melanoma. The current study correlated the gene expression signature scores to actual clinical outcomes in cases from the first validation study. RNA was extracted from 127 archival formalin-fixed paraffin-embedded tissue sections of melanocytic lesions. Gene expression was measured using quantitative reverse transcription polymerase chain reaction and a weighting algorithm was used to generate a numeric score. Gene expression test results were compared to histopathological diagnoses and development of local recurrence, sentinel lymph node metastases, and distant metastases. Sixty-five lesions were diagnosed histopathologically as melanoma. Fourteen developed metastases. Gene expression test results were malignant in 61/65 (93.8%) lesions (including all lesions that metastasized), indeterminate in 2/65 (3.1%) lesions, and benign in 2/65 (3.1%) lesions. The remaining 62 lesions were diagnosed as benign by histopathology. Gene expression test results were benign in 48/62 (77.4%), indeterminate in 7/62 (11.3%), and malignant in 7/62 (11.3%). There was a strong correlation between the gene expression signature test results and clinical outcomes. All lesions that metastasized were correctly identified by the test as malignant melanoma.