A 60-year-old woman presented with diffuse lymphadenopathy. Diagnostic and staging work-up showed that the patient had diffuse small cleaved cell lymphoma (diffuse poorly differentiated lymphocytic lymphoma) with associated histiocytes (lymphoepithelioid cell lymphoma) by the Kiel classification system. Immunohistologic staining showed a T suppressor cell tumour phenotype. Cytogenetic studies revealed the Philadelphia chromosome (Ph1). On DNA studies, the breakpoint cluster region (BCR) gene was not rearranged suggesting that the Ph1 involvement was not identical to that seen in chronic myelogenous leukemia (CML). This case is presented because of the rarity of Ph1 in lymphoid malignancies, particularly in those of T-cell origin, and because of its potentially adverse implications.