We reviewed 1,143 lymphoid neoplasm of pediatrics, adolescents, and young adults (PAYA), and analyzed the distribution of T/NK-cell neoplasms according to the 5th WHO classification. Of these 1,143 lymphoid neoplasms, 937 (82%) were non-Hodgkin lymphomas, including 685 (73.1%) B-cell and 252 (26.9%) T/NK-cell neoplasms. T/NK-cell neoplasms were more frequent in 0-to-21-year-old patients (38.8%) than in 22-to-39-year-old patients (20.7%; P<0.001). Precursor T-cell neoplasms were more common in 0-to-21-year-old patients (P<0.001). A total of 178 mature T/NK-cell neoplasms included 63 (35.4%) cutaneous T-cell lymphoid proliferations/lymphomas (CTCLs), 45 (25.3%) anaplastic large cell lymphomas ( 41 were ALK-positive), 33 (18.5%) extranodal NK/T-cell lymphomas, 16 (9%) peripheral T-cell lymphoma-NOS, 14 (7.9%) EBV-positive T/NK-cell lymphoid proliferations/lymphomas of childhood (EBVTNKLPDs), and 7 others. Proportions of mature T/NK-cell neoplasms were different between age groups (P=0.007). CTCLs included 18 (10.1%) subcutaneous panniculitis-like T-cell lymphomas (TCLs), 18 (10.1%) mycosis fungoides, 15 (8.4%) primary cutaneous CD30-positive T-cell LPDs (one 7-year-old boy with NPM1::TYK2 fusion), 4 primary cutaneous gdTCLs, 2 primary cutaneous CD8-positive aggressive epidermotropic cytotoxic TCLs (one 9-year-old boy with NUP214::JAK2 fusion), and 6 others. Distribution of CTCLs showed no significant difference among age groups. Although EBVTNKLPD was more common in 0-to-21-year-old patients than in 22-to-39-year-old patients (14.5% vs. 2.9%, respectively), there was no significant difference in the frequency of overall EBV-associated T/NK-cell neoplasms between age groups. This study showed a characteristic distribution of mature T/NK-cell neoplasms in PAYA.
