Pediatric Plasma Cell Neoplasms: A Population-Based Study

Introduction Plasma cell neoplasms are exceptionally rare in the pediatric population; the demographic characteristics and the clinical outcomes of plasma cell neoplasms in this population are currently poorly understood. The aim of this study was to provide a comprehensive analysis of pediatric plasma cell neoplasms, based on the United-States Surveillance, Epidemiology, and End Results (SEER) program registries. Materials and Methods All pediatric patients (aged less than 20 years) diagnosed with a malignant plasma cell neoplasm were retrieved from the SEER Program database (18 registries), collecting patient records between 2000 and 2018. The plasma cell neoplasm type, sex, age at diagnosis, year of diagnosis, race and origin, primary disease site, follow-up duration, and vital status at the last known contact were retrieved and analyzed. Results The age-adjusted incidence rate of plasma cell neoplasms for 1,000,000 person-years was 0.06 for the pediatric population (compared with 90.6 for the adult population). The types of pediatric plasma cell neoplasms predominantly consisted of plasmacytomas, with 11 solitary extraosseous plasmacytoma (42.3%) and 7 solitary bone plasmacytoma (26.9%), while plasma cell myelomas represented only a minority of the neoplasms (8 patients; 30.8%). Most plasmacytomas were localized in the head and neck region. Hispanic patients represented 50% of the pediatric plasma cell neoplasm cases (but only 11.1% of adult cases, P < .01). Female-to-Male ratio was 1.36. Five-year overall survival rates were 88.2% (95% confidence interval [95% CI]: 74.2%-100%) for pediatric plasmacytoma and 36.5% (95% CI: 12.4%-100%) for pediatric plasma cell myeloma (P = .013). Conclusion This first population-based study of pediatric plasma cell neoplasms underlines the rarity of this entity and demonstrates its unique characteristics, including the significant predominance of plasmacytomas, of female patients, and of patients from hispanic origin, and the poor clinical outcomes of pediatric plasma cell myeloma patients.