Primary cutaneous CD30+ lymphoproliferative disorders (LPDs), including lymphomatoid papulosis (LyP), anaplastic and nonanaplastic CD30+ large-cell lymphoma, and borderline cases, comprise a clinical and histologic spectrum. Primary cutaneous and primary nodal CD30+ anaplastic large-cell lymphomas (ALCLs) are distinct clinical entities that have identical morphologic features but differ in age of onset, immunophenotype, and prognosis. It can be difficult to distinguish primary cutaneous from nodal ALCLs that secondarily involve the skin, which is important because these diseases differ significantly in response to treatment and clinical outcome. The t(2;5) chromosomal translocation is highly associated with primary CD30+ ALCL of nodal origin. The possible occurrence of t(2;5) in primary cutaneous CD30+ LPDs has not been studied extensively, and it remains to be determined if expression of this translocation can be used to distinguish primary cutaneous ALCL from nodal ALCL that secondarily involves the skin. To address these issues, we studied 43 cases of cutaneous and nodal CD30+ LPDs using reverse transcriptase-polymerase chain reaction (RT-PCR) and/or immunohistochemistry. We found no evidence for the t(2; 5) translocation in 14 cases of primary cutaneous CD30+ LPDs, which included 10 cases of LyP, three cases of primary cutaneous CD30+ ALCL, and one borderline case. These findings were in marked contrast to CD30+ ALCL of nodal origin, in which 19 of 29 (66%) cases were positive for t(2;5), including all five cases with secondary skin involvement. Our results support the hypothesis that (1) primary cutaneous CD30+ LPDs (including LyP) and primary nodal ALCL are distinct diseases that differ in clinical behavior and pathogenesis and (2) differential expression of t(2;5) can help to distinguish between primary cutaneous CD30+ LPDs and ALCL of nodal origin.