Utility of Immunohistochemistry in the Diagnosis of Pleuropulmonary and Mediastinal Cancers: A Review and Update

CONTEXT.—

Immunohistochemistry has become a valuable ancillary tool for the accurate classification of pleuropulmonary and mediastinal neoplasms necessary for therapeutic decisions and predicting prognostic outcome. Diagnostic accuracy has significantly improved because of the continuous discoveries of tumor-associated biomarkers and the development of effective immunohistochemical panels.

OBJECTIVE.—

To increase the accuracy of diagnosis and classify pleuropulmonary neoplasms through immunohistochemistry.

DATA SOURCES.—

Literature review and the author's research data and personal practice experience.

CONCLUSIONS.—

This review article highlights that appropriately selecting immunohistochemical panels enables pathologists to effectively diagnose most primary pleuropulmonary neoplasms and differentiate primary lung tumors from a variety of metastatic tumors to the lung. Knowing the utilities and pitfalls of each tumor-associated biomarker is essential to avoid potential diagnostic errors.

Utility of Immunohistochemistry in the Diagnosis of Pleuropulmonary and Mediastinal Cancers: A Review and Update

Context

Immunohistochemistry has become an indispensable ancillary tool for the accurate classification of pleuropulmonary and mediastinal neoplasms necessary for therapeutic decisions and predicting prognostic outcome in the era of personalized medicine. Diagnostic accuracy has significantly improved because of the continuous discoveries of tumor-associated biomarkers and the development of effective immunohistochemical panels.

Objective

To increase the accuracy of diagnosis and classify pleuropulmonary neoplasms through immunohistochemistry.

Data Sources

Literature review, authors' research data, and personal practice experience.

Conclusions

This review article has shown that appropriately selecting immunohistochemical panels enables pathologists to effectively diagnose most primary pleuropulmonary neoplasms and differentiate primary lung tumors from a variety of metastatic tumors to the lung. The discovery of new mutation-specific antibodies identifying a subset of specific gene-arranged lung tumors provides a promising alternative and cost-effective approach to molecular testing. Knowing the utilities and pitfalls of each tumor-associated biomarker is essential to avoiding potential diagnostic errors.

Napsin-A, TTF-1, EGFR, and ALK Status Determination in Lung Primary and Metastatic Mucin-Producing Adenocarcinomas

Pulmonary mucin-producing adenocarcinomas may be indistinguishable on conventional histology from a metastasis, as thyroid transcription factor-1 (TTF-1) expression often is lacking and KRAS mutations are widely present even in extrapulmonary sites. Few data have been reported on the diagnostic role of napsin-A and epidermal growth factor receptor (EGFR) and anaplastic lymphoma kinase (ALK) gene alterations in this challenging differential diagnosis. Seventy-seven surgically resected cases, including 53 primary and 24 metastatic tumors from different sites, were evaluated for napsin-A, TTF-1, and ALK by immunohistochemistry and for EGFR mutations by direct sequencing. Overall, napsin-A expression in primary lung mucin-producing adenocarcinomas was 36% (8% mucinous, 17% colloid, 87.5% solid, and 100% signet ring cell) and TTF-1 expression reached an overall figure of 42% (12.5% mucinous, 33% colloid, 87.5% solid, and 100% signet ring cell). Metastatic mucinous adenocarcinomas did not react with napsin-A or with TTF-1. All primary and metastatic tumors lacked EGFR mutations, while a single case of signet ring cell lung adenocarcinoma showed ALK expression and rearrangement at fluorescent in situ hybridization analysis. Napsin-A has a lower sensitivity compared with TTF-1 in primary mucin-producing adenocarcinomas of the lung. However, both antibodies have an absolute specificity, being always negative in metastatic mucinous adenocarcinomas. EGFR mutations and ALK translocation or expression are exceedingly rare in mucin-producing adenocarcinomas of the lung, resulting unnecessary as diagnostic tool in this setting.

Immunohistochemistry: applications to the evaluation of lung and pleural neoplasms: part 1

Immunohistochemistry has come to occupy a key position among the armamentarium of tools pathologists apply to the evaluation of lung and pleural neoplasms. This technique uses antibodies that bind to specific antigens, usually proteins, enabling microscopic detection of the antigens. Over the last several decades, an impressive array of antibodies has become commercially available, and many of these antibodies have become integrated into the routine practice of pathology. Evaluation of tissue or cytology samples with these antibodies can facilitate determination of tumor type and site of origin. Comments citing results of immunohistochemical staining with these antibodies frequently appear in pathology reports and may be difficult to translate for those less familiar with the technique. This review presents, in two parts, common diagnostic applications of immunohistochemistry, with information about strategies taken for frequently encountered differential diagnostic scenarios. This, the first of two parts, offers a basic overview of the technique and discusses its applications in the diagnosis of common primary lung carcinomas.