Can cytology reliably subtype non‐small cell lung carcinomas?

Abstract

Organization classification of lung tumours, recommends the subtyping of non-small cell lung carcinomas (NSCLC) into squamous cell carcinoma (SQC) and adenocarcinoma (ADC) histology. [1][2][3] In other words, emphasis is put on differentiating NSCLC into ADC and SQC in cytology as well as small biopsy specimens as a standard of care for accurate targeted therapy of these patients. It is therefore not sufficient to separate small cell lung carcinoma (SCLC) from NSCLC; further distinction of NSCLC is warranted. Morphology with or without immunocytochemistry (ICC) is a cornerstone of the correct identification of SCLC and the distinction of NSCLC into SQC and ADC. 4,5 Having stated so, it is also true that morphologically clearcut glandular and squamous differentiation is recognised in only 50%-60% of NSCLC cases. 6 The remaining cases require ancillary testing in the form of mucin stains and/or immunophenotyping by lineage-specific markers such as thyroid transcription factor-1 (TTF-1), Napsin A, p40 and cytokeratin 5/6 (CK5/6). 7,8

Agreement Between Mucicarmine-Stained Bronchial Brushing and Bronchial Biopsy in Subtyping Non-small Cell Lung Carcinoma

“…The strength of agreement between the findings of bronchial brushing and bronchial biopsy was found to be moderate in this study. This result is in accordance with the studies by Patel et al and Jain et al, which showed fair-to-high concordance between these modalities in subtyping NSCLC [2,8].…”

“…Herein, 30-50% of NSCLCs were not classified further and were designated by the term NSCLC-not otherwise specified (NSCLC-NOS) [3,7]. With the identification of molecular differences and the emergence of target therapy for different subtypes of NSCLC differentiating squamous cell carcinoma (SCC) from adenocarcinoma (ADC) has become necessary [3,5,7,8]. Prediction of the improved response of epidermal growth factor receptor (EGFR)-positive ADC to tyrosine kinase inhibitor and pemetrexed and potential toxicity of bevacizumab in SCC emphasize the need for this differentiation [1][2][3].…”

“…To save the tissue for necessary molecular testing the use of only one SCC marker (p63 or p40) and one ADC marker (thyroid transcription factor 1, TTF-1) with/without histochemical stain for mucin is recommended [1,3,[7][8][9][10].…”

Editorial

“…A thorough appraisal of the possibilities offered by cytology in this area is provided by Jain & Bubendorf. 1 Cytopathology approaches, when used in conjunction with immunohistochemistry, can provide accurate and speedy diagnosis and classification of lung cancers, enabling patient management.…”

“…Small cell carcinomas are managed differently to pulmonary squamous and adenocarcinomas in the advanced disease setting, and a small cell carcinoma diagnostic label may be all that is required currently for appropriate management decisions to be made, although this may change in the near future. A thorough appraisal of the possibilities offered by cytology in this area is provided by Jain & Bubendorf 1 . Cytopathology approaches, when used in conjunction with immunohistochemistry, can provide accurate and speedy diagnosis and classification of lung cancers, enabling patient management.…”