Equivocal atypia in respiratory cytology can be a diagnostic challenge. In such cases fluorescence in situ hybridization (FISH) may be used for the analysis of chromosomal aberrations and often allows a reliable distinction of benign and malignant cells.
An online picture gallery of 30 respiratory cytologic preparations comprising 23 specimens with equivocal cytology as well as 5 positive and 2 negative controls was prepared (www.unibas.ch/patho/lungenzyto/loesung). The final diagnoses were confirmed by clinical follow-up or biopsy or both. Each of the illustrated cell groups was analyzed by multitarget FISH after PAP image capturing and automatic relocalization.
The online questionnaire was completed by 137 cytomorphologists from all continents. The control cases were assessed accurately to a significantly higher percentage than the equivocal cases. In equivocal cases participants more often made false-positive than false-negative diagnoses. In 2 patients with benign conditions (tuberculosis and pulmonary capillaritis) the rate of false-positive answers was remarkably high (31.4% and 62.8% respectively). The result of the 20 best-performing participants for the 5 cases with the highest percentage of inaccurate answers was not better than if they had chosen their answer by chance.
These data illustrate that single cells or cell clusters of a subgroup of equivocal lung cytology are a diagnostic challenge even for highly experienced morphologists. Internet-based tests are able to reveal limitations of cytomorphology.