Recommendations for Ancillary Testing

Abstract

Prior to the emergence of targeted therapeutics, conventional ancillary testing in respiratory cytology has included microbiologic culture for infectious agents, special stains and/or immunocytochemistry (ICC) for establishing a cytomorphologic diagnosis, and flow cytometry and/or fluorescence in situ hybridization (FISH) for hematolymphoid neoplasms. With the increasing use of molecular diagnostic assays for predictive, prognostic, and therapeutic purposes in lung carcinoma patients, the need for ancillary testing of lung cytology specimens has also expanded. Biomarker testing for tyrosine kinase inhibitors (TKIs) and immunotherapies using molecular and immunohistochemical methods now play a pivotal role in the management of non-small cell lung carcinoma (NSCLC) patients (Lindeman, Cagle, Aisner, Arcila, Beasley, Bernicker, et al. Updated molecular testing guideline for the selection of lung cancer patients for treatment with targeted tyrosine kinase inhibitors: guideline from the College of American Pathologists, the International Association for the Study of Lung Cancer, and the Association for Molecular Pathology. Arch Pathol Lab Med, 2018). Since a large fraction of these patients present at an advanced stage of disease with unresectable tumors, cytology samples are often the only source of tissue for diagnosis and biomarker testing. Therefore, ancillary testing in lung cytology has expanded beyond its conventional role into a variety of molecular (nucleic acid and protein based) assays that have been integrated into routine cytopathology practice and play a key role in patient care. The Papanicolaou Society of Cytopathology System for Reporting Respiratory Cytology has therefore developed some recommendations for the use of ancillary testing in lung cytology (Layfield, Roy-Chowdhuri, Baloch, Ehya, Geisinger, Hsiao, et al. Utilization of ancillary studies in the cytologic diagnosis of respiratory lesions: the Papanicolaou Society of Cytopathology consensus recommendations for respiratory cytology. Diagn Cytopathol 44:1000–9, 2016).