Characterization of Morphologic and Cytochemical Staining Properties of Exogenous Materials Mimicking Fungal Organisms Encountered in Skin Biopsies

Background Exogenous materials may be encountered in skin biopsies as contamination. Contamination may occur during the biopsy procedure in the clinic or during tissue processing in the laboratory. Although the experienced pathologist may often instinctively ignore clear examples of contamination, such tissue may be a source of confusion for young pathologists and those in training. Foreign materials can typically be recognized as exogenous by morphology, polarizability, and the presence or absence of a tissue reaction, but we have rarely encountered situations in which exogenous materials could be misinterpreted as organisms, either by their morphologic appearance or staining properties. Methods Exogenous materials used during skin biopsy and grossing were embedded in a nonhuman tissue scaffold and prepared into histologic slides. Hematoxylin and eosin (H&E), periodic acid-Schiff with diastase, and Grocott methenamine silver stains were performed, and each material was evaluated under polarized microscopy. Results Exogenous materials were divided into the following 3 categories with shared morphologic appearances and staining properties: suture materials, plant-based materials, and synthetic materials. Conclusion We present a comprehensive characterization of the morphologic and cytochemical staining properties of multiple exogenous materials that may contaminate a skin biopsy. This characterization will aid the pathologist by providing a mechanism to identify potential contaminants in skin biopsies.