Lung Carcinoma Predictive Biomarker Testing by Immunoperoxidase Stains in Cytology and Small Biopsy Specimens: Advantages and Limitations

Abstract

Context.-In the burgeoning era of molecular genomics, immunoperoxidase (IPOX) testing grows increasingly relevant as an efficient and effective molecular screening tool. Patients with lung carcinoma may especially benefit from the use of IPOX because most lung carcinomas are inoperable at diagnosis and only diagnosed by small tissue biopsy or fine-needle sampling. When such small specimens are at times inadequate for molecular testing, positive IPOX results still provide actionable information.Objective.-To describe the benefits and pitfalls of IPOX in the detection of biomarkers in lung carcinoma cytology specimens and small biopsies by summarizing the currently available commercial antibodies, preanalytic variables, and analytic considerations.Data Sources.-PubMed.Conclusions.-Commercial antibodies exist for IPOX detection of aberrant protein expression due to EGFR L858R mutation, EGFR E746_A750 deletion, ALK rearrangement, ROS1 rearrangement, and BRAF V600E mutation, as well as PD-L1 expression in tumor cells. Automated IPOX protocols for ALK and PD-L1 detection were recently approved by the Food and Drug Administration as companion diagnostics for targeted therapies, but consistent interpretive criteria remain to be elucidated, and such protocols do not yet exist for other biomarkers. The inclusion of cytology specimens in clinical trials would expand patients' access to testing and treatment, yet there is a scarcity of clinical trial data regarding the application of IPOX to cytology, which can be attributed to trial designers' lack of familiarity with the advantages and limitations of cytology. The content of this review may be used to inform clinical trial design and advance IPOX validation studies.

Best Practices Recommendations for Diagnostic Immunohistochemistry in Lung Cancer

“…Although the large variety of transport media, prefixatives, and cell block protocols do not appear to cause systematic problems on immunostaining according to a previous survey, 131 recent analyses pinpoint to specific challenges related to preanalytical factors in cell blocks, especially with ethanol or methanol prefixation. 29,132 In addition to absent or near-absent expression of TTF1 with CytoLyt fixative, 29 nearly half (43%) of the 30 antibodies tested on the Cellient cell block system (Hologic) failed initial validation with use of the conditions established for FFPE tissue specimens on the Ventana Benchmark XT immunostainer (Ventana Medical Systems, Tucson, AZ). 133 Non-cell block cytologic specimens consist of a variety of preparations, which include air-dried and alcohol-fixed smears, cytospins (Thermo Fisher Scientific), ThinPrep (Hologic), or SurePath (Becton Dickinson, Franklin Lakes, NJ) liquid-based preparations.…”

Immunocytochemistry for predictive biomarker testing in lung cancer cytology

“…Although approximately 51% and 75% of cytology laboratories in the United States and Europe, respectively, reported using non‐CB preparations for diagnostic ICC in surveys from 6 to 7 years ago, their use for ICC has likely declined more recently—particularly in the United States, where commercial laboratories do not accept smears for ICC. There is a paucity of articles outlining best practice guidelines for ICC, and many perform diagnostic ICC without adequate validation or quality control measures . In an external quality assessment program conducted in Europe, a high quality of immunostaining, regardless of methods or fixatives, was observed on a variety of cytology preparations received from different laboratories, and there is good evidence that with appropriate modifications in analytical factors, ICC on non‐CB preparations can be equivalent to ICC on FFPE CB sections …”

New Cell Block Method to Enhance the Cellular Yield in Mucous and/or Bloody Samples

“…Having a panel of immunostained slides is nowadays mandatory to correctly name various tumors, especially in pulmonary cytology [17]. In our series, we have tested a wide spectrum of immunostainings and proved the suitability of new in-house techniques for good immunoreactivity.…”