Non Pathogenic Fungal Contaminants in Cytological Specimens: Beware the Imitation

Identification of nonpathogenic fungal contaminants is of utmost importance to ensure diagnostic accuracy in cytology. At times, these elements mimic pathogenic organisms and mislead the cytologist. In this study, we share our experience with the presence of various fungal contaminants in cytology slides that pose frequent diagnostic challenges.

The main objective of this study was to identify nonpathogenic fungal contaminants in cytopathology specimens.

Records of all cytology specimens (fluids, PAP smears, and FNA samples) received in our institute over a period of 1-year were included in the initial analysis. Fluid samples showing presence of fungal elements included non-sterile and sterile fluids such as bronchoalveolar lavage, gastric lavage, urine, CSF, synovial fluid, pleural, pericardial, and ascitic fluids. Apart from these, their presence was noted in conventional and liquid based cervical cytology specimens. Most of these cases had microbiological culture correlation. Simultaneously, the glass slides and reconstituted stains in our lab were also tested for the presence of fungi.

The percentage of samples showing positive fungal elements was calculated.

More than 11,000 cytology specimens were received over a span of 1 year in sterile containers and smears were prepared from various clinical specialities. The most common contaminants identified were Fusarium species. The second most prevalent contaminant was Alternaria, which may be causative agent of phaeohyphomycosis. Microbiological cultures of these specimens were often negative but yielded respective fungal species at other times.

Fungal contaminants were observed to be the most ubiquitous and mischievous imitators which can perplex the cytologists.