WT1 (6F-H2)

Anti-WT1 is useful in the differential diagnosis of pulmonary malignancies in that up to 93% of malignant mesotheliomas (nuclei) are labeled with this antibody. In contrast, the nuclei of lung adenocarcinomas are not labeled with this product (0 of 50 in a recent study).1-5 However, cytoplasmic labeling of lung adenocarcinomas may be observed. The differential diagnosis of abdominal papillary carcinomas can be problematic. Anti-WT1 labels 93% of serous ovarian carcinomas and 0% (nuclei) of mucinous carcinomas of the ovary and pancreato-biliary carcinomas.6 Anti-WT1 can also be utilized in the differential diagnosis of small round cell tumors as 100% of desmoplastic small round cell tumors and 70% of nephroblastomas (Wilm’s tumor) are positive (nuclei) for this marker. Tumors such as Ewings sarcoma/PNET, neuroblastomas, rhabdomyosarcomas, and rhabdoid tumors are negative. Occasionally cytoplasmic labeling may be seen in these tumors, however.7