Although primary cutaneous ALCL (pc-ALCL) is currently classified as a subtype of primary cutaneous T-cell lymphoma, due to the large anaplastic and pleomorphic morphology together with CD30 expression in the malignant cells, this review also discusses the pathobiological features of this disease entity. The gene discussed is TNFRSF8; the disease is primary cutaneous T-cell non-Hodgkin lymphoma.