Evaluation of Crizotinib Treatment in a Patient With Unresectable GOPC-ROS1 Fusion Agminated Spitz Nevi

Importance

Spitz nevi are benign melanocytic neoplasms that classically present in childhood. Isolated Spitz nevi have been associated with oncogenic gene fusions in approximately 50% of cases. The rare agminated variant of Spitz nevi, thought to arise from cutaneous genetic mosaicism, is characterized by development of clusters of multiple lesions in a segmental distribution, which can complicate surgical removal. Somatic single-nucleotide variants in theHRASoncogene have been described in agminated Spitz nevi, most of which were associated with an underlying nevus spilus. The use of targeted medical therapy for agminated Spitz nevi is not well understood.

Observations

A girl aged 30 months presented with facial agminated Spitz nevi that recurred rapidly and extensively after surgery. Owing to the morbidity of further surgery, referral was made to a molecular tumor board. The patient’s archival nevus tissue was submitted for extended immunohistochemical analysis and genetic sequencing. Strong ROS1 protein expression was identified by immunohistochemistry. Consistent with this, analysis of whole-genome sequencing data revealedGOPC-ROS1fusions. These results indicated likely benefit from the oral tyrosine kinase inhibitor crizotinib, which was administered at a dosage of 280 mg/m²twice daily. An excellent response was observed in all lesions within 5 weeks, with complete flattening after 20 weeks.

Conclusions and Relevance

Given the response following crizotinib treatment observed in this case, the kinase fusion was believed to be functionally consequential in the patient’s agminated Spitz nevi and likely the driver mutational event for growth of her nevi. The repurposing of crizotinib forGOPC-ROS1Spitz nevi defines a new treatment option for these lesions, particularly in cases for which surgery is relatively contraindicated.