Objectives: Primary mediastinal large B-cell lymphomas (PMLBCLs) are aggressive lymphomas with characteristic clinical, morphologic, and immunophenotypic features. "Double-hit" (DH) lymphomas are B-cell neoplasms characterized by a translocation involving MYC and either BCL2 or BCL6 . In the indexed literature, there are no reported cases of PMLBCL associated with DH or triple-hit events. Methods: Herein, we present a case of a 15-year-old girl with PMLBCL who had typical clinical, morphologic, and immunophenotypic features. Results: Fluorescent in situ hybridization studies showed rearrangements involving MYC and BCL6 . We also excluded the possibility of a reciprocal t(3;8) (3q27;8q24) BCL6 / MYC translocation. Conclusions: This case expands the current spectrum of lymphomas subtypes in which DH can be found and supports the rationale for cytogenetic testing for DH abnormalities in all cases of aggressive large B-cell lymphomas regardless of subtype.