Academy of Medical Sciences of I.R. Iran Archives of Iranian Medicine 1029-2977 29 3 2026 03 01 Patterns and Temporal Dynamics of Pediatric Solid Malignant Tumors: Insights from a 27-Year Referral Center Cohort in Iran (1996–2022) 133 147 10.34172/aim.35172 EN Maryam Kazemi Aghdam https://orcid.org/0000-0001-9948-417X Yalda Nilipour Seiedehparnian Taghvaei Bibi Shahin Shamsian Samin Alavi Nader Momtazmanesh Peyman Eshghi Gholamreza Ebrahimisaraj https://orcid.org/0000-0002-2086-2164 Mehdi Sarafi Leili Mohajerzadeh Javad Ghoroubi Mohsen Rouzrokh Ahmad Khaleghnejad Tabari Journal Article 10.34172/aim.35172 2025 09 26 2026 02 10 Introduction: Pediatric solid malignant tumors cause a growing concern with regional variations. Long-term data from Iran are limited. This study examined the temporal trends and distribution of these tumors over 27 years in a large referral cohort, focusing on patterns rather than absolute national incidence. Methods: We retrospectively analyzed 2,579 children diagnosed with solid malignant tumors at Mofid Children’s Hospital, Tehran (1996–2022). Demographics, tumor types, and temporal patterns were assessed. Joinpoint regression evaluated temporal trends using population-standardized and crude rates as analytic denominators for trend assessment. Age–Period–Cohort models were fitted for lymphomas, central nervous system (CNS), and sympathetic nervous system (SNS) tumors. Age-standardized incidence rates (ASIRs) and incidence rate ratios (IRRs) were calculated. Results: Children aged 1-4 years predominated (45.1%). CNS and SNS tumors were most common (40.8%), followed by lymphomas (16.7%). Referral-based population-standardized diagnosis rates increased significantly over time (1996–2022; AAPC=4.81%, P<0.001), with similar trends for crude rates (AAPC=6.03%, P<0.001). CNS and SNS tumors showed the steepest and most consistent increases. Age–period–cohort analyses indicated dominant calendar period effects, particularly for CNS and SNS tumors, while age effects were tumor-specific and cohort patterns were variable. Incidence rate ratios demonstrated higher referral-based diagnosis rates in 2014–2022 across all age groups, most pronounced for CNS and SNS tumors in younger children. Tumor composition shifted over time, with increasing CNS and SNS contributions. Conclusion: Over 27 years, referral-based pediatric solid tumor diagnoses increased significantly, driven by CNS and SNS tumors. Our findings underscore complex temporal dynamics in referral-based pediatric solid tumor diagnoses and highlight the need for enhanced surveillance and etiologic research.