Aims: To evaluate HBME-1, WT1, calretinin and MOC-31 in the differential diagnosis of pleural mesothelioma and adenocarcinoma of the lung.
Methods and results: Paraffin-embedded formalin-fixed blocks from six reactive pleuras, 42 mesotheliomas and 40 adenocarcinomas were used. Sections were stained for Leu-M1, HBME-1, calretinin, WT1 and MOC-31. Leu-M1 was positive or equivocal in 34% of mesotheliomas and in 78% of adenocarcinomas; reactive pleuras were all negative. HBME-1 was positive or equivocal in 76% of mesotheliomas and in 73% of adenocarcinomas; five reactive pleuras were positive. Calretinin was positive or equivocal in 92% of mesotheliomas and in 73% of adenocarcinomas; two reactive pleura were equivocal and four were positive. WT1 was positive or equivocal in 72% of mesotheliomas (excluding autopsy cases) and in 20% of adenocarcinomas; all reactive pleuras were positive. MOC-31 was positive or equivocal in 5% of mesotheliomas and in 90% of adenocarcinomas; all reactive pleuras were negative. The reaction with Leu-M1 was graded as equivocal in 25% of the adenocarcinomas. All 24 of the autopsy cases of mesothelioma were negative for WT1 and in many operative specimens only the periphery was stained.
Conclusions: Neither calretinin nor HBME-1 are sufficiently discriminatory to be of use, even as members of a panel of antibodies. WT1 shows some promise, but it cannot be used on autopsy material. The utility of MOC-31 is confirmed, and outperforms Leu-M1.