Background: Blastomycosis is caused by a dimorphic fungus that can be difficult to diagnose in certain situations. The disease is sometimes serious and can be deadly. Diagnosis by fungal serology and urinary antigens is not easy to establish and unreliable. Culture is also time-consuming and is not easy to perform. Thus, documentation of such an organism on cytology offers a quick and cost-effective alternative. This report describes for the first time identification of the ‘negative image’ of Blastomyces budding yeast. Case: A 79-year-old man presented with a left lung nodule associated with mediastinal and hilar lymphadenopathy. Fine needle aspiration was performed, and a ‘negative image’ of a yeast with wide base budding was noted on Diff-Quik (DQ)-stained smears. Blastomyces species were confirmed with periodic acid-Schiff fungal stain. Additionally, the fungal capsule contained focally polarizable material on Congo red stain and lacked mucin with mucicarmine stain. Conclusion: Blastomyces yeast forms can be easily identified with DQ staining by their ‘negative image’. This feature can be utilized as a quick and cost-effective cytological characteristic to further triage these specimens for confirmation. The information can be of great value to clinicians in making appropriate clinical decisions.

Keywords:
Blastomycosis, Negative image, Diff-Quik stain
© 2011 S. Karger AG, Basel
2011
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