Summer Spores of Birch Rust Fungus in Papanicolaou Smears from Healthy Mass Screening Participants

Abstract

To evaluate the origin and identification of mysterious particles in Papanicolaou smears from healthy, asymptomatic women participating in a local mass screening program. The material consisted of 16,000 cerricovaginal smears studied at the cytology laboratory of Pathology Laboratory of South-Western Finland Ltd. Unidentified particles were found in four apparently independent smears. All the slides were rescreened, but no further positive cases were found. Several swab samples were collected from the investigation room, but all were negative. Attempts at identification included numerous consultations. A telepathology consultation with the Cellular Division, Armed Forces Institute of Pathology, Washington, D.C., U.S.A., was conducted. Another teleconsultation with the reference laboratoryfor intestinal parasites in Iceland was conducted. Finally, the Aerobiology Unit, University of Turku, was consulted. The aerobiologist suggested that the particles were most probably summer spores of birch rust fungus (Melampsoridium betulinum). To confirm this we obtained a reference specimen of the fungus from the herbarium at the University of Turku. The morphology of the spore particles was identical to that in the cervicovaginal smears, proving that the smears were contaminated with birch rust fungus spores. Birch rust is ubiqutitous in Finland. Outside the hospital window there is a wide lawn behind which, at a distance of 70 m, there is a forest of birch trees. It is most likely that the rust spores flew in through the open window, to settle down on the surface of material that was used in sample taking. Airborne dust may cause misleading and surprising artefacts. Protection of specimens and instruments against dust should minimize the problem.