The importance of accurately characterizing lymphoproliferative disease.

The primary cutaneous CD30-positive (CD30+) T-cell lymphoproliferative disorders are a group of largely indolent diseases that manifest as nodules or tumors of the skin. The European Organisation for Research and Treatment of Cancer (EORTC) has developed a modification of the World Health Organization (WHO) lymphoma classification system that specifically categorizes these entities. According to Willemze et al, the CD30+ diseases include primary anaplastic large-cell lymphoma (ALCL), primary CD30+ lymphoproliferative disorder, and ymphomatoid papulosis (LyP).[1] Collectively, these are a common type of cutaneous T-cell lymphomas (CTCL), comprising 25% of cases. Often confused with more aggressive T-cell lymphomas with similar histopathologic features, these diseases are difficult to diagnose and poorly understood. The differential diagnosis of CD30+ CTCL includes the CD30+ lymphoproliferative disorders (primary cutaneous ALCL, LyP), secondary cutaneous lymphomas (systemic ALCL, systemic CD30+ peripheral T-cell lymphoma), CD30+ mycosis fungoides variants, and reactive skin conditions (arthropod bites, scabies, drug eruptions, atopic dermatitis, and viral infections).