A PRKCA-Fused Blue Melanocytoma Expressing a Truncated ALK Isoform.

Melanocytic tumors are categorized into "common," "Spitz," and "blue" types based on distinct genetic profiles, as recognized in the latest WHO classification. In this report, we present the first case of a PRKCA-fused blue melanocytoma ALK-positive in a 13-year-old girl, who exhibited a dome-shaped cutaneous lesion on the tibia. The tumor demonstrated an intriguing immunostaining with ALK1A4 antibody. Targeted RNA sequencing revealed a PRKCA fusion without ALK rearrangement. But, further investigations uncovered ALK alternative transcripts resulting from an alternative transcription initiation (ATI). While the ALK truncated isoform (ALK ATI) has been identified in a small subset of melanomas, its presence in Spitz or blue tumors has not previously been documented.

Abstract from PubMed