Technical aspects of the use of cytopathological specimens for diagnosis and predictive testing in malignant epithelial neoplasms of the lung

Abstract

Lung cancer is a leading cause of cancer mortality worldwide, 1 and for at least 50 years, primary pathological diagnosis has been based on small biopsies and cytopathological specimens. Until approximately 20 years ago, a simple binary categorisation of small cell and non-small cell lung carcinoma (NSCLC) was, in most cases, sufficient for diagnosis and treatment.However, recent years have seen a rapidly rising proportion of cases of NSCLC amenable to increasingly targeted therapy, initially based on the differential response to systemic treatment of tumours of squamous or glandular differentiation 2 then on the presence of particular mutations in the EGFR gene. [3][4][5] Subsequently, further "driver mutations" have been identified with an increasing percentage having associated treatments. Finally, there is an expanding therapeutic repertoire of immune checkpoint inhibitors with eligibility determined, at least in part, by the expression of immune modulators such as Programmed Death Ligand-1 (PD-L1). 6 In the USA, it is now mandatory to test for EGFR mutations, ALK and ROS1 translocations, and expression of PD-L1. In addition, it is recommended to test for BRAF and MET mutations and RET and NTRK fusions. 7,8 In the UK, for patients with NSCLC of stage IIIB and above, treatments that target genomic abnormalities in EGFR, ALK, ROS1, and quantified expression of PD-L1 are standard-of-care 9 ; those targeting NTRK fusions are approved under certain circumstances 10,11 and those applied to RET and MET abnormalities are currently being assessed by the National Institute for Health and Care Excellence. 12,13 Treatments for a wide variety of other genomic abnormalities are being studied in clinical trials [14][15][16] and adjuvant treatments for

Editorial

“…This is often overlooked, but Maddox and Smart outline how to make the most of the samples obtained and discuss practical issues such as specimen types, ROSE, handling processes and the vagaries of molecular testing. 3 Cytopathology samples have not enjoyed strong support from some sectors of the lung oncology community, with concerns raised about their suitability for biomarker profiling. Some of this reticence is the result of misconstruction of the fact that cytopathology-type samples are rarely, if ever, accepted in clinical trials when companion biomarkers are being developed.…”

“…Suffice to say, cytopathology‐type samples can be perfectly adequate for molecular/biomarker profiling, provided, of course, that there is sufficient tumour content in the sample and that the sample has been handled and processed in a way that is permissive for all the testing that may be required. This is often overlooked, but Maddox and Smart outline how to make the most of the samples obtained and discuss practical issues such as specimen types, ROSE, handling processes and the vagaries of molecular testing 3 . Cytopathology samples have not enjoyed strong support from some sectors of the lung oncology community, with concerns raised about their suitability for biomarker profiling.…”

Cell block‐based RNA next generation sequencing for detection of gene fusions in lung adenocarcinoma: An institutional experience

“…Even surgically resectable adenocarcinomas are usually diagnosed by cytological specimens. It has been shown that cytology samples can be used for molecular testing to determine the most effective therapies 4 …”

“…The feasibility of non‐formalin fixed cytology specimens for RNA sequencing of lung adenocarcinomas has been shown in some recent studies 10,11 . Although residual cell pellets, smear slides and supernatants can be used for molecular testing, cell blocks are the most common source in daily practice 4,10,12–16 . However, Ramani, et al reported only a 45% success rate using cell blocks due to insufficient cellularity and/or suboptimal RNA quality 10 …”

“…It has been shown that cytology samples can be used for molecular testing to determine the most effective therapies. 4 Various methods can be used for the detection of these gene fusions, including immunohistochemistry, fluorescence in situ hybridisation (FISH), DNA based hybrid capture sequencing, RNA based transcript fusion detected by reverse transcription-polymerase chain reaction (RT-PCR) and targeted next-generation sequencing (NGS). 1,[5][6][7] Only a limited number of studies have investigated the use of cytological specimens for RNA-based NGS.…”