Tumors of uncertain differentiation: report of two cases of Pleomorphic Dermal Sarcoma

Background: Atypical Spitz tumours (AST) are rare melanocytic lesions with overlapping features of benign Spitz nevi and spitzoid melanoma, making their diagnosis and management challenging.These tumours often exhibit histopathological and molecular variability, which further complicates their differentiation from malignant counterparts.Paediatric patients tend to present with distinct clinical and histological patterns, including thicker lesions and unique molecular features.Despite advances in diagnostic techniques, there is no standardised approach to the management of AST and sentinel lymph node biopsy (SLNB) remains controversial.This study aims to provide insight into age-related differences in AST characteristics and outcomes using a large, single-centre cohort spanning two decades.Methods: A retrospective study was performed on 248 patients diagnosed with Spitz nevi or AST at the Veneto Oncology Institute between 2002 and 2022.Clinical, histopathological and molecular data were collected and analysed, focusing on tumour thickness, mitotic rate, presence of kamino bodies and molecular markers such as S100, SOX 10, Melan A expression.Paediatric cases (<18 years) were compared with adults in terms of clinical presentation, histopathological features and outcomes.Statistical analyses included several tests to assess the relationships between age, tumour thickness, recurrence and survival outcomes.Results: Younger patients (<18 years) had significantly thicker lesions than adults (>18 years) (mean thickness: 1.88 mm vs. 1.17 mm, p=0.0018).An inverse correlation was observed between age and lesion thickness (r=-0.316,p=0.00035), indicating that younger patients tend to have thicker lesions.Lesions with higher mitotic rates were observed more frequently in patients undergoing sentinel lymph node biopsy (SLNB).No significant differences in recurrence rates were observed between paediatric and adult cases undergoing or not undergoing SLNB.Conclusions: The management of AST requires a personalised approach that incorporates clinical, histopathological and molecular data.Paediatric cases present with distinct clinical and histological features, necessitating age-specific strategies.These findings highlight the importance of multidisciplinary care models to optimise the diagnosis and management of AST in all age groups.