An atypical morphologic presentation of Coccidioides spp. in fine-needle aspiration of lung

Infection due to Coccidioides spp., a dimorphic fungal pathogen, usually presents as a chronic pulmonary disease, occasionally with pulmonary nodules. On cytology, large spherules filled with endospores are typically seen. We report an unusual case of coccidioidomycosis in a 39-year-old female from an area nonendemic for Coccidioides and without other known risk factors for infection. Fine-needle aspiration of the patient's cavitary lung lesion revealed Coccidioides spp., which demonstrated atypical delicate septate hyphal forms and chains of conidia, with none of the large spherules typical of Coccidioides spp. Atypical hyphal and other forms of Coccidioides spp. have been reported in several studies, primarily from biopsy or tissue resection specimens. However, this is the first case to our knowledge that the organism has presented solely as conidial and atypical hyphal forms in an aspirated specimen. Pathologists who are unfamiliar with this atypical hyphal formation may misdiagnose the organism as several different fungi, including Aspergillus spp. or Fusarium spp. It is important to differentiate among fungi, as antifungal treatments may vary. Cytologists should be aware of the diverse morphologies demonstrated by Coccidioides spp. and include this organism in their differential diagnosis, even in patients seemingly devoid of pertinent risk factors.