AbstractLymphomas are currently categorized according to their origin from a B or T lymphocyte. Immature and less commonly mature (peripheral) lymphomas may harbor rearrangements of both the B‐ and T‐cell antigen receptor genes (dual genotype or bigenotype). Rarely, cells in lymphoma with a single genotype simultaneously express both B‐ and T‐cell markers (biphenotypic lymphomas). We discuss the diagnostic and clinical implications in the case of a 42‐yr‐old female with a peripheral CD30+ lymphoma that displayed both characteristic B‐ and T‐cell surface antigens and clonal rearrangement of B‐ and T‐cell antigen receptor gene loci. Simultaneous nuclear expression of the transcription factor gene PAX5 suggested that this major driver of B‐cell differentiation did not preclude expression of CD3ε, generally assumed to be a T‐cell associated antigen.