Primary cutaneous CD30(+) lymphoproliferative disorders.

Primary cutaneous CD30(+) lymphoproliferative disorders are the second most common group of cutaneous T-cell lymphomas (CTCL) and include lymphomatoid papulosis (LyP) and primary cutaneous anaplastic large T-cell lymphoma (cALCL). Both disease entities share overlapping clinical, histopathological, and molecular features, thus representing a spectrum of cutaneous CD30(+) lymphoproliferative disorders. LyP may be distinguished from cALCL by clinicopathological correlation. In some patients, both diseases may coexist at initial diagnosis or develop over the course of the disease. Mycosis fungoides (MF), the most common CTCL, is not considered a primary cutaneous CD30(+) lymphoproliferative disorder, but may occur in some LyP patients. In addition, LyP-like lesions may develop in MF patients. However, this is frequently a manifestation of MF rather than a representation of two different disease entities. Caution also has to be taken in the setting of transformed MF with lesions expressing CD30, as they may be mistaken for either LyP or cALCL, resulting in an inadequate therapeutic approach.