AbstractAnaplastic lymphoma kinase (ALK) positive diffuse large B‐cell lymphoma (DLBCL) is a rare subtype of non‐Hodgkins lymphoma. Five such cases have been described in children. We present a 9‐year‐old boy, in whom diagnosis of DLBCL has been established in addition to congenital multiple enchondromatosis. Immunohistopathological evaluation of tumor biopsy established the final diagnosis of ALK + DLBCL. The clathrin gene (CLTC)‐ALK fusion underlying aberrant expression of ALK in the present case was demonstrated by interphase fluorescence in situ hybridization (FISH) using break‐apart rearrangement probes for ALK and CLTC. The disease in this patient was highly resistant to applied chemotherapy regimens and to radiotherapy. Analysis of the disease course in our patient and review of other cases reported previously show that ALK + DLBCL can be an aggressive malignancy that can be cured with conventional chemotherapy protocols only at stage of localized disease. Pediatr Blood Cancer © 2005 Wiley‐Liss, Inc.