Atypical Spitzoid Neoplasms in Childhood: A Molecular and Outcome Study

The natural history of atypical Spitz neoplasms remains poorly understood, resulting in significant patient and clinician anxiety. We sought to better characterize outcomes that correlated with molecular features by performing a prospective cohort study of pediatric atypical spitzoid neoplasms in which fluorescence in situ hybridization studies were obtained for diagnosis. Cases with sufficient tissue underwent additional retrospective assessment for translocations in ALK, NTRK1, BRAF, RET, and ROS1. Among 246 total patients assessed, 13% had a positive fluorescence in situ hybridization result. Follow-up data was available in 85 patients. Two patients had a recurrence of whom 1 had distant metastasis. Both patients had homozygous deletions in 9p21. Homozygous deletions in 9p21 significantly correlated with recurrence of disease (P = 0.027). Fifteen (36%) of 42 cases were found to have a kinase fusion protein. However, the presence of kinase fusions was nonprognostic of recurrence (P > 0.99). This study was limited by the availability and length of follow-up data and the number of adverse outcomes. The majority of atypical spitzoid neoplasms in childhood have indolent behavior. Although the subgroup of patients with homozygous deletions in 9p21 is at higher risk for aggressive clinical behavior, their prognosis seems considerably better than similarly staged conventional melanoma.