Clinicopathological Features and Prognosis of Pediatric Mastocytosis: A 15-Year Experience with Emphasis on Disease Evolution.

BACKGROUND: Mastocytosis is characterized by abnormal accumulation of mast cells in one or multiple organs. Pediatric-onset mastocytosis varies from adult type in the clinical manifestations and disease courses. OBJECTIVE: To better understand the pediatric variants from adult mastocytosis, we performed a thorough study of mastocytosis subtypes. METHODS: We retrospectively reviewed patients with mastocytosis beginning at ≤17 years of age who were evaluated in the Department of Dermatology between 2009 and 2025. Diagnoses and subtype classifications were established according to the 2022 World Health Organization (WHO) diagnostic criteria. Clinicopathological features, immunophenotypes, clinical outcomes, and potential prognostic factors were analyzed. RESULTS: Fifty-two patients were included, with a male to female ratio of 2.25:1. Maculopapular cutaneous mastocytosis (MPCM) was the most common subtype, followed by cutaneous mastocytoma, diffuse cutaneous mastocytosis (DCM) and systemic mastocytosis. Among MPCM patients, 60.47% were classified as p-MPCM and 39.53% as m-MPCM. Compared to m-MPCM, p-MPCM showed more frequent extremity involvement (P=0.0037) and laboratory abnormalities. CD2 was expressed in 74.42% of pediatric mastocytosis, while CD25 and CD30 were expressed in a few congenital lesions with high mast cell burden. Four patients (11.76%) achieved complete remission, and 11 patients (32.35%) showed partial remission, whereas 19 patients (55.88%) had persistent lesions with non-remission or worsening condition. Kaplan-Meier analysis revealed no significant association between clinicopathological variables with clinical outcome. CONCLUSION: Chinese pediatric patients with mastocytosis in our cohort tend to have isolated CM without systemic involvement, significant predilection for male, and persistent clinical course with limited favorable outcomes. Pediatric mastocytosis exhibited distinct clinical manifestations and immunophenotypes in contrast to adult mastocytosis and Caucasian cohorts, suggesting age-related and population-related differences in disease evolution.