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Case Reports in Pathology
Volume 2017 (2017), Article ID 6714549, 5 pages
Case Report

PAX8 Distinguishes Diffuse Large B-Cell Lymphoma Mimicking Sarcoma

1Department of Pathology, Brigham and Women’s Hospital and Harvard Medical School, Boston, MA, USA
2Diagnose Anatomia Patologica e Citopatologia, Rio de Janeiro, RJ, Brazil

Correspondence should be addressed to Michelle S. Hirsch

Received 3 February 2017; Accepted 2 May 2017; Published 28 May 2017

Academic Editor: Dimosthenis Miliaras

Copyright © 2017 Michelle S. Hirsch and Alessandra F. Nascimento. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


PAX8 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.