THE USE OF LIQUID-BASED CYTOLOGY IN DIAGNOSIS OF BASAL CELL CARCINOMA AND ACTINIC KERATOSIST - The CYT-BAK study
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Background: Ahead of new non-invasive treatments of non-melanoma skin cancer, cytology has proven beneficial and may become the diagnostic method of choice as it results in little tissue disfiguration and thus a superior cosmetic outcome at the sampling site compared to biopsy. Liquid-based cytology (LBC) is fast, easy, and inexpensive in use and may be more beneficial than conventional cytology as it provides instant fixation and preservations of collected cells. Aims: To evaluate the quality of LBC with the use of ThinPrep®Pap test as a diagnostic tool of BCC and AK and to compare the diagnostic performance of LBC with histopathology. Methods: This is a prospective, blinded, single-centre pilot study approved by the Regional Committee for Medical Research Ethics. It was performed at the Department of Dermatology and Department of Pathology and Medical Genetics, St. Olavs Hospital, Trondheim University Hospital. Patients with primary, histologically verified BCC and AK who met the inclusion criteria were recruited to the study during PDT-treatment at the outpatient clinic from September through December 2015. After initial light curettage, a Medscand®Cytobrush was used to collect cells from the tumours. The cells were instantly fixated by rapid transfer to the ThinPrep® Pap test container. The cytological specimens were evaluated by a pathologist and cytologist without knowledge of the histology diagnoses and classified as BCC, AK, other diagnosis or non-evaluable. Cytodiagnostic results were compared with the diagnosis in the histopathology report (the gold standard). Results: A total of 13 lesions (8 BCC, 5 AK) were included of which 5 samples were classified as non-evaluable. Cytodiagnosis agreed with histopathology in 6 of the 8 BCC cases, and in 2 of the 5 AK cases. Sensitivity and specificity of LBC for diagnosis of BCC was 75% and 100% (95% CI: 0.35-0.97 and 0.48-1.00), respectively. Sensitivity and specificity for diagnosis of AK was 40% and 100% (95% CI: 0.05-0.85 and 0.63-1.00), respectively. Conclusion: The results suggest that LBC using ThinPrep®Pap test and Medscand®Cytobrush following curettage has a too low sensitivity for routine diagnostic use for diagnosis of BCC and AK. However, when the cell material was representative a correct diagnosis was made in all cases.