The activation marker CD30 is useful in the diagnosis Hodgkin and non-Hodgk
in lymphomas. It has also described in nonhematopoietic tumors, including p
ancreatic carcinomas, salivary gland tumors, and embryonal carcinomas. We r
eport a case of malignant mesothelioma with intense CD30 positivity. This f
inding has not previously been described and is important in broadening the
differential diagnosis of a CD30(+) cohesive large cell malignancy.