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Volume 2012 (2012), Article ID 494571, 16 pages
Review Article

Detection of Microorganisms in Granulomas That Have Been Formalin-Fixed: Review of the Literature Regarding Use of Molecular Methods

Department of Pathology and Laboratory Medicine, Emory University, Atlanta, GA 30322, USA

Received 19 November 2012; Accepted 11 December 2012

Academic Editors: G. Marucci and D. Sanglard

Copyright © 2012 Jeannette Guarner. 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.


Granuloma is an organized aggregate of immune cells that under the microscope appear as epithelioid macrophages. A granuloma can only be diagnosed when a pathologist observes this type of inflammation under the microscope. If a foreign body or a parasite is not observed inside the granuloma, stains for acid-fast bacilli and fungi are ordered since mycobacteria and fungi are frequently the cause of this type of inflammation. It is calculated that 12 to 36% of granulomas do not have a specific etiology and many have wondered if with new molecular methods we could reduce this number. This paper will summarize the frequently known causes of granulomas and will present the recent literature regarding the use of molecular techniques on tissue specimens and how these have helped in defining causative agents. We will also briefly describe new research regarding formation and function of granulomas and how this impacts our ability to find an etiologic agent.