Pancreatic metastases of renal clear cell carcinoma: a clinicopathological study of 11 cases with special emphasis on the usefulness of PAX2 and mesothelin for the distinction from primary ductal adenocarcinoma of the pancreas.

To determine whether PAX2 and mesothelin immunohistochemistry add additional diagnostic value in discriminating between pancreatic metastasis of renal clear cell carcinoma (PMRCC) and primary ductal adenocarcinoma of the pancreas (PDAC). We retrospectively collected tissue from PMRCC and PDAC. Eleven cases of PMRCC registered at Lille University Hospitals from 2001 to 2010 were included. Eleven cases of PDAC were randomly selected from our files. A comparative immunohistochemical study with anti-PAX2, anti-mesothelin, and the classical renal antibodies anti-CD10 and anti-vimentin was performed on PMRCC and PDAC. We found that PMRCC displays a clinical presentation that might mimic primary pancreatic tumor, as PMRCC presented as a solitary mass in 8 cases and appeared a long time after diagnosis of a renal tumor (12.8 years, mean for metachronous metastasis). By immunohistochemistry we observed that PAX2, mesothelin, CD10 and vimentin stainings were noted in 10/11 (91%), 0/11 (0%), 11/11 (100%) and 7/11 cases (64%), respectively, among 11 PMRCC cases. All PDACs displayed diffuse mesothelin (100%) expression without PAX2 and vimentin (0%) staining, whereas CD10 was noted in 4/11 cases (36%). These data suggest that in difficult diagnostic cases both PAX2 and mesothelin immunohistochemical study may be useful in discriminating between PMRCC and primary pancreatic carcinoma.