![]() The advantages of obtaining these specimens have created a series of diagnostic challenges because of the limited amount of tissue obtained and the architectural distortion produced by these new procedures. Furthermore, advances in diagnostic radiology and in patient support (such as platelet transfusions, etc) have allowed greater ability to pursue specific diagnoses by collecting tissue biopsy specimens from body sites formerly not available for histopathologic examination. In addition, diagnosis of infection versus colonization with these fungi is a frequent problem that has important treatment implications for these patients. Today, fungi previously considered nonpathogenic, including mucoraceous genera (formerly called zygomycetes) and a variety of both hyaline and dematiaceous molds, are commonly seen in immunocompromised patients. Prior to the 21st century, bloodstream infections were more frequently caused by Candida spp., and agents of invasive pulmonary infections included primarily endemic mycoses and Aspergillus spp. Thus, a shift in the mycoses encountered in the health care setting has occurred. At-risk populations for opportunistic fungal infections or disseminated endemic fungal infections include patients who have received transplants, those prescribed immunosuppressive and chemotherapeutic agents, HIV-infected patients, premature infants, the elderly, and patients undergoing major surgery. Some of the changes in endemic fungal infections can be attributed to climate changes, extension of human habitats, ease of travel, and shifting populations. In addition, techniques such as laser microdissection will be useful to detect the now more frequently recognized dual fungal infections and the local environment in which this phenomenon occurs.įungal infections are becoming more frequent because of expansion of at-risk populations and use of treatment modalities that permit longer survival of these patients ( 109). Alternate techniques have been used to determine the specific agent present in the histopathologic specimen, including immunohistochemistry, in situ hybridization, and PCR. The pathology report should also include a comment stating the most frequent fungi associated with that morphology as well as other possible fungi and parasites that should be considered in the differential diagnosis. Therefore, histopathologic diagnosis should be primarily descriptive of the fungus and should include the presence or absence of tissue invasion and the host reaction to the infection. However, there are very few instances where the morphological characteristics of fungi are specific. ![]() Because histopathologic examination of tissues detects fungal invasion of tissues and vessels as well as the host reaction to the fungus, it is and will remain an important tool to define the diagnostic significance of positive culture isolates or results from PCR testing. Summary: Fungal infections are becoming more frequent because of expansion of at-risk populations and the use of treatment modalities that permit longer survival of these patients.
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