Cell pellet from fixative medium of transbronchial lung biopsy sample improves lung cancer ancillary test

Abstract

Objectives: Lung cancer tissue obtained using small biopsies are relatively fragile, leaving behind some tiny tissue fragments or cell clusters in the fixative medium that are difficult to collect for processing as a paraffin-embedded tissue block. Usually, the cellular component of the residual fixative medium is discarded as medical waste as per routine laboratory protocol. No protocol exists for utilizing the cellular component of the residual fixative medium after processing the tissue blocks to improve lung cancer ancillary testing. This study aimed to undercover the potential value of these samples for lung cancer diagnosis and targeted therapy development.

Materials and methods: A protocol was developed for cell pellet sample collection from the residual fixative medium of a transbronchial forceps lung biopsy sample. Tumour cell number and fraction in a paired cell pellet and matching formalin-fixed paraffin-embedded tissue section were evaluated from 324 non-smallcell lung carcinoma (NSCLC) cases. We defined the adequacy of the cell pellet for molecular analysis as ≥ 200 tumour cells and ≥ 10 % tumour cells. Real-time polymerase chain reaction and next-generation sequencing were performed on adequate cell pellet samples.

Results: We discovered that the fixative medium of most transbronchial forceps lung biopsy samples was enriched in tumour cells. Among 324 biopsy samples, 70 (21.6%) exhibited inadequate formalin-fixed paraffin-embedded tissue sections, whereas 53 (75.7%) yielded adequate cell pellet samples. Somatic mutations detected in the formalin-fixed paraffin-embedded tissue section samples were also detected in the matching cell pellets.

Conclusions: Cell pellets collected from the fixative medium of thoracic small biopsies are a beneficial supplemental material for ancillary testing. Combined use of cell pellets with traditional tissue-based samples can enhance the detection rate of informative mutations in patients with advanced NSCLC.

Keywords: Ancillary testing; Cell pellet; Fixative medium; Mutation detection; Non-small cell lung carcinoma; Transbronchial forceps lung biopsy.