[Primary cutaneous CD30+ lymphoproliferative disorders]

CD30+ lymphoproliferative disorders are the most common group of cutaneous T-cell lymphomas after mycosis fungoides and its subtypes. This group includes lymphomatoid papulosis and CD30+ anaplastic large-cell lymphoma; these 2 entities are the extremes of a spectrum with numerous intermediate varieties in which it is not possible to establish a clear diagnosis based on clinical and histopathologic criteria. CD30+ lymphoproliferative disorders must be differentiated from other lymphoproliferative diseases with CD30+ cells in the tumor infiltrates, such as mycosis fungoides or Hodgkin disease, and also from other inflammatory conditions or nonhematological neoplasms that can include this cell type, such as pityriasis lichenoides et varioliformis acuta or certain mesenchymal tumors (CD30+ pseudolymphomas). In contrast to their systemic homologues, which arise in the lymph nodes, CD30+ lymphoproliferative disorders generally have a good prognosis. It is very important to exclude the presence of a lymphoma of systemic origin with extralymphatic spread, as the prognosis and treatment are different.