The prognostic value of pathologic characteristics of childhood ALK-positive anaplastic large-cell lymphomas (ALCL), such as histologic subtypes, immunophenotype, and presence of the t(2;5) translocation or its variants, was assessed.

All 375 patients with systemic ALK-positive ALCL included in an international trial launched by the European Intergroup for Childhood Non-Hodgkin's Lymphoma were reviewed by an international panel of pathologists based on conventional hematoxylin and eosin–stained and immunostained sections and classified according to the 2001 WHO classification.

A small-cell (SC) or lymphohistiocytic (LH) component was observed in 114 (32%) of 361 patients, whereas ALCL of common type was diagnosed in 235 (65%) of 361 patients. Regarding the histologic subtyping of patients within the two categories of ALCL (with v without SC/LH component), the concordance between the national and international reviews was quite good, with a κ index equal to 0.67 (95% CI, 0.57 to 0.75). The presence of an SC/LH component was significantly associated with a high risk of failure (hazard ratio [HR], 2.0; 95% CI, 1.3 to 3.0; P = .002) in the multivariate analysis controlling for clinical characteristics, as well as the perivascular pattern (HR, 1.7; 95% CI, 1.1 to 2.7; P = .01), whereas CD3 positivity was significantly associated with a high risk of failure only in univariate analysis.

Our study, which to our knowledge includes the largest series of childhood systemic ALK-positive ALCL so far, demonstrates the adverse prognostic value of SC and/or LH morphologic features. Combining these histologic characteristics with other biologic or clinical factors might have a high potential for future risk stratification and treatment.