Abstract
Immunohistochemistry is a widely available technique that is less challenging and can provide clinically meaningful results quickly and cost-efficiently in comparison with other techniques. In addition, immunohistochemistry allows for the evaluation of cellular localization of proteins in the context of tumor structure. In an era of precision medicine, pathologists are required to classify lung cancer into specific subtypes and assess biomarkers relevant to molecular-targeted therapies. This review summarizes the hot topics of immunohistochemistry in lung cancer, including (i) adenocarcinoma vs squamous cell carcinoma; (ii) neuroendocrine markers; (iii) ALK, ROS1, and EGFR; (iv) PD-L1 (CD274); (v) lung carcinoma vs malignant mesothelioma; and (vi) NUT carcinoma. Major pitfalls in evaluating immunohistochemical results are also described.
Highlights
In an era of precision medicine, immunohistochemistry plays a critical role in the classification of tumors into subtypes and for assessing biomarkers for timely and accurate therapeutic decision-making [1,2,3,4,5]
Lung cancer is the leading cause of cancer-related deaths worldwide, regardless of gender. It is categorized into two main groups: small cell lung carcinoma (SCLC, 15% of all lung cancers) and non-SCLC (NSCLC, 85% of all lung cancers)
A solid carcinoma without keratinization or intercellular bridges, but with immunohistochemical positivity for “squamous cell carcinoma (SqCC) markers”, such as p40, CK5/6, and TP63 (p63), is diagnosed as SqCC. These modifications using immunohistochemical evaluations have markedly minimized the proportion of non-small cell lung carcinoma (NSCLC) diagnosed as large cell carcinoma [19]
Summary
In an era of precision medicine, immunohistochemistry plays a critical role in the classification of tumors into subtypes and for assessing biomarkers for timely and accurate therapeutic decision-making [1,2,3,4,5]. A solid carcinoma without keratinization or intercellular bridges, but with immunohistochemical positivity for “SqCC markers”, such as p40, CK5/6, and TP63 (p63), is diagnosed as SqCC. These modifications using immunohistochemical evaluations have markedly minimized the proportion of NSCLC diagnosed as large cell carcinoma [19]. It should be noted that a significant number of SqCCs or adenocarcinomas show a positivity for TTF-1 (clone SPT24) or TP63, respectively. As another pitfall, trapped benign pneumocytes (positive for TTF-1 and Napsin A) and tumor-infiltrated macrophages (positive for Napsin A) should not be misinterpreted
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