FISH analysis for p16/CDKN2A revealed the absence of deletion in one case (14.3%) of epithelioid and one case (16.7%) of biphasic mesotheliomas, heterozygous deletion in three cases (42.8%) of epithelioid and one case (16.7%) of biphasic mesotheliomas, and homozygous deletion in three cases (42.8%) and four cases (66.7%) of epithelioid and biphasic mesotheliomas, respectively. The gene discussed is CDKN2A; the disease is malignant biphasic mesothelioma.