TERT Promoter Mutations Are Predictive of Aggressive Clinical Behavior in Patients with Spitzoid Melanocytic Neoplasms

Spitzoid neoplasms constitute a morphologically distinct category of melanocytic tumors, encompassing Spitz nevus (benign), atypical Spitz tumor (intermediate malignant potential), and spitzoid melanoma (fully malignant). Currently, no reliable histopathological criteria or molecular marker is known to distinguish borderline from overtly malignant neoplasms. Because TERT promoter (TERT-p) mutations are common in inherently aggressive cutaneous conventional melanoma, we sought to evaluate their prognostic significance in spitzoid neoplasms. We analyzed tumors labeled as atypical Spitz tumor or spitzoid melanoma from 56 patients with available follow-up data for the association of TERT-p mutations, biallelic CDKN2A deletion, biallelic PTEN deletion, kinase fusions, BRAF/NRAS mutations, nodal status, and histopathological parameters with risk of hematogenous metastasis. Four patients died of disseminated disease and 52 patients were alive and disease free without extranodal metastasis (median follow-up, 32.5 months). We found TERT-p mutations in samples from the 4 patients who developed hematogenous metastasis but in none of tumors from patients who had favorable outcomes. Presence of TERT-p mutations was the most significant predictor of haematogenous dissemination (P < 0.0001) among variables analyzed. We conclude that TERT-p mutations identify a clinically high-risk subset of patients with spitzoid tumors. Application of TERT-p mutational assays for risk stratification in the clinic requires large-scale validation.