Hirsch, MichelleNascimento, Alessandra F.2017-07-242017Hirsch, Michelle S., and Alessandra F. Nascimento. 2017. “PAX8 Distinguishes Diffuse Large B-Cell Lymphoma Mimicking Sarcoma.” Case Reports in Pathology 2017 (1): 6714549. doi:10.1155/2017/6714549. http://dx.doi.org/10.1155/2017/6714549.http://nrs.harvard.edu/urn-3:HUL.InstRepos:33490771PAX8 is important for embryogenesis of the thyroid, Müllerian system, and upper urinary/renal tract, and expression of PAX8 has been described in carcinomas from each of these sites. The sensitivity and specificity of the polyclonal PAX8 antibody in a large cohort of epithelial tumors as well as lymphomas have been previously determined, the latter because polyclonal PAX8 is known to be immunoreactive in nonneoplastic B-cell lymphocytes which are often used as the positive internal control for immunohistochemistry. In this case report, PAX8 was a diagnostic clue for revising a previous diagnosis of unclassified high grade sarcoma to diffuse large B-cell lymphoma. This case report demonstrates a pitfall for PAX8 immunoreactivity and acts as a reminder that lymphoma should be included in the differential diagnosis of a PAX8 positive, epithelial cell marker negative tumor of unknown primary origin.en-USJournal Article2017-07-2410.1155/2017/6714549