Utility of small biopsies for diagnosis of lung nodules: doing more with less

Abstract

Small biopsies obtained by core needle or bronchoscopy are commonly used for diagnosis of lung nodules. This review provides guidance in two key areas of interpretation of small lung biopsies. The first part answers common questions regarding the immunohistochemical subclassification of non-small cell lung carcinomas that cannot be classified by standard criteria on hematoxylin-eosin-stained sections of small lung biopsies. The second part discusses common benign entities that can be diagnosed in core needle biopsies of lung nodules, such as granulomatous inflammation, parenchymal scars and organizing pneumonia. The approach to cases in which malignant cells are absent and features of a specific benign diagnosis are lacking is also addressed.

Non-Small-Cell Lung Carcinoma Subtyping on Cytology without the Use of Immunohistochemistry – Can We Meet the Challenge?

“…One can argue that when diagnosis is attempted based on morphology alone, observer variation can pose a serious problem. Confirmation of the diagnosis by a small panel of immunostains can be a useful method of supporting morphology, keeping in mind that large panels of immunohistochemical stains may not provide an advantage over routine light-microscopic diagnosis or when the primary immunostains have failed [6,7,9]. Several recent publications have addressed the use of a limited panel of markers for distinguishing between adenocarcinomas and squamous-cell carcinoma.…”

“…The discovery of epidermal growth factor receptor (EGFR) mutation and its prediction of response to EGFR tyrosine kinase inhibitors (TKIs) in adenocarcinoma patients have shifted the goal from not just identifying non-squamous non-small-cell lung carcinomas but also at providing the accurate diagnosis of adenocarcinomas [1,2,3,4,5,6,7,9]. As most lung cancer patients present at an advanced unresectable stage at diagnosis, small biopsies and cytological samples are frequently the only available diagnostic material.…”

“…Several recent publications have addressed the use of a limited panel of markers for distinguishing between adenocarcinomas and squamous-cell carcinoma. The use of at most a panel of 2 immunostains has been recommended in order to preserve as much tissue as possible [6]. …”

“…With the increasing demand of cytological diagnosis and the subtyping of non-small-cell lung carcinoma, immunohistochemistry is increasingly incorporated to achieve 100% cytological accuracy. Many recent studies have highlighted the pitfalls of immunostaining interpretation including the coexpression of thyroid transcription factor 1 (TTF-1) and p63 in adenocarcinomas, TTF-1 and napsin A positivity in squamous-cell carcinoma (owing to the entrapped normal bronchial epithelial cells) and p63-negative squamous-cell carcinoma [6,7]. These pitfalls and the need to strategically use the cytology specimens have necessitated the readdressing of morphological diagnosis of adenocarcinoma versus squamous-cell carcinoma by the cytopathologists.…”

New Lung Adenocarcinoma Classification in Daily Practice

“…In the past, there was no clinical demand for subclassifying NSCLC as this had no specific impact on therapy. However, at the present time, subclassification of NSCLC has significant treatment implications (8). One of the most important steps in the management of NSCLC patient is the distinction between adenocarcinoma and squamous cell carcinoma because, in the new area of targeted therapies, at present only patients with adenocarcinoma are eligible for tyrosine kinase inhibitor (TKI) therapy (if the tumour presents an EGFR mutation), or a pemetrexed or bevacizumab-based chemotherapy regimen.…”