The difficulty in interpreting gene expression profiling in BAP-negative melanocytic tumors

Area of Science:

• Dermatopathology
• Oncology
• Genetics

Background:

• BAP-negative melanocytic tumors are rare and poorly understood, with concerns about potential malignant transformation.
• Their clinical significance and biologic potential require further investigation.

Purpose of the Study:

• To evaluate the utility of a 23-gene expression profiling (23-GEP) test in differentiating BAP-negative melanocytic tumors from melanoma.
• To characterize the biologic potential of these challenging lesions.

Main Methods:

• Retrospective analysis of twenty BAP-negative melanocytic tumors using 23-GEP testing.
• Comparative genomic hybridization (aCGH) was performed on select cases.
• Histopathological and immunohistochemical analyses were also conducted.

Main Results:

• The 23-GEP test yielded "malignant" signatures in 4 cases, "benign" in 15, and "indeterminate" in 1.
• aCGH results conflicted with 23-GEP in two cases, suggesting benignity despite a "malignant" 23-GEP signature.
• In one case, a "benign" 23-GEP result was contradicted by aCGH, supporting melanoma assessment.
• Histopathology could not exclude evolving melanoma in two cases with "benign" 23-GEP results.

Conclusions:

• BAP-negative melanocytic tumors present a significant diagnostic challenge for dermatopathologists.
• The 23-GEP test may have limited utility in distinguishing these tumors from spitzoid melanoma compared to aCGH.
• Further research is needed to establish definitive diagnostic and prognostic tools for these lesions.