Atypical Spitz Tumors: Age-Related Clinicopathological Features, Management Strategies, and Long-Term Follow-Up Outcomes in a 20-Year Retrospective Cohort Study

Background: Atypical Spitz tumors (ASTs) represent a heterogeneous spectrum between Spitz nevi and Spitz melanoma. Objective: To analyze age-related Clinicopathological features of ASTs and evaluate prognostic factors, including histological aggressiveness and sentinel lymph node status, with recurrence-free survival (RFS) as the primary endpoint. Materials and Methods: A retrospective cohort study was conducted on 190 consecutive patients diagnosed with ASTs between January 2002 and December 2022 at two Italian tertiary referral centers. Patients were stratified into four prespecified age groups (≤18, 19–25, 26–39, ≥40 years). Clinical, histological, and surgical data were collected, and survival analyses were performed using Kaplan–Meier estimates and non-parametric tests. Results: Median follow-up was 40 months (IQR 18–79; 640 person-years). Lesions most affected the lower limbs (52%). Breslow thickness and mitotic activity decreased significantly with age (mean thickness 2.33 mm in children vs 0.88 mm in adults ≥40 years; p < 0.001). Sentinel lymph node biopsy (SLNB) was performed in 30% of re-excised cases, with node positivity in 42% of pediatric patients versus 9% in adults. However, SLNB positivity did not predict recurrence. Only one local recurrence was observed, in an adult ≥40 years, later reclassified as melanoma. No distant metastases or melanoma-related deaths occurred. Five-year RFS was 100% in patients ≤39 years and 98% (95% CI 94–100) in patients ≥40 years. Conclusions: Over this 20-year cohort, ASTs demonstrated an overall indolent clinical course across all age groups. Despite greater thickness and mitotic activity in pediatric patients, tumors behaved indolently, while the only aggressive case in adults reflected initial misdiagnosis. These findings suggest conservative excision without routine SLNB in pediatric patients, and a cautious, multidisciplinary approach for adults with atypical features. The retrospective design, referral-center setting, low event rate, and limited molecular testing represent study limitations.