Atypical Spitz Tumor (Spitz Melanocytoma) With Lymph Node Metastasis and Long-Term Clinical Follow-Up.

Spitz tumors are clinically and histologically challenging because of their close histologic resemblance to melanomas. Differentiating metastatic atypical Spitz tumors from melanoma has been a controversial issue for many decades. Diagnosis relies on expert pathologist review and a host of immunohistochemical and genomic testing including gene fusions in ALK, ROS, and NTRK, which has been informative in diagnosing and classifying these challenging lesions. Evidence suggest that atypical Spitz tumors associated with regional lymph node metastasis have good prognosis and do not spread to internal organs, however, cases of childhood melanomas (often with TERT mutations) can occur, often with a fatal outcome. Therefore, making a conclusive diagnosis is crucial when treating patients. In this study, we report a girl diagnosed with atypical Spitz tumor with lymph node metastasis at the age of 10 years. She has shown no recurrence after 20 years of follow-up. The formalin-fixed, paraffin-embedded tissue was retrospectively analyzed by next-generation sequencing and additional immunohistochemistry. PRAME immunohistochemistry was negative, as were ALK and ROS. No BRAF or TERT mutations were identified. No pathogenic or likely pathogenic variant was identified on testing lymphocyte DNA for familial malignant melanoma, including CDKN2A, CDK4, and BAP1 and a panel of 79 genes associated with childhood solid tumors.