The differential diagnosis of anaplastic large-cell lymphoma includes other CD30+ large cell proliferations such as viral infection, drug reactions, other lymphomas (Hodgkin's lymphoma and B-, T- and NK-cell lymphomas), carcinoma, melanoma and granulocytic sarcoma.101–104 In these other processes, CD30 is often present in only a subset of cells and the staining pattern may be weak with a focal or diffuse cytoplasmic pattern rather than the strong membrane and Golgi CD30 expression seen in virtually every cell in anaplastic large-cell lymphoma. This evidence concerns the gene TNFRSF8 and viral infectious disease.