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INTRODUCTION

A pathologist experienced in thoracic oncology is an essential member of the thoracic team. The pathologist plays a fundamental role in the preoperative, intraoperative, and postoperative diagnostic and staging evaluation of the tissue specimens. Traditionally, the surgical pathologist’s role was confined to diagnostic and staging evaluation. However, with the advent of new innovations in molecular methodologies and precision medicine, they now play a pivotal role in the provision of prognostic and predictive biomarker data for targeted therapies. Thus, there has been a paradigm shift in the role of the pathologist, and the scope of their duties has broadened considerably. Yet, for the foreseeable future, their traditional expertise will remain an important component of precision medicine.1 The goal of tissue examination varies depending on the clinical setting. In the preoperative and intraoperative settings, the pathologist is mainly focused on accurate diagnosis and molecular profiling, whereas, in the postoperative setting, the focus shifts to staging.

The primary tumor and/or lymph nodes are evaluated preoperatively with the aim of obtaining accurate diagnostic and staging information to guide therapeutic decisions. The preoperative evaluation includes examination of one of the following specimens: bronchial brushings, bronchial washings, fine-needle aspiration biopsy (examined by the cytopathologist), core needle biopsy, endobronchial biopsy, and transbronchial biopsy (examined by the surgical pathologist). The first step in the preoperative biopsy examination in the context of a lung nodule is to evaluate whether the sample is benign or malignant. If malignant, the next step is to determine the histopathologic subtype and origin of the tumor. This usually requires the use of appropriate immunohistochemical stains. Tissue is used not only for the diagnostic workup but also for a wide range of biomarker testing. The biomarkers commonly used for the lung cancer panel include EGFR, ALK, ROS1, and PDL-1. Most lung biopsies are extremely small. Because 70% of lung carcinomas are inoperable, these tiny fragments are often the only material available for examination. Thus, the initial consideration is to optimally use the tissue by pragmatically choosing the order of testing, which is tailored to each individual case. The focus then turns to fulfilling the need for accurate diagnosis and prognostic/predictive information.2

The intraoperative evaluation of the surgical pathology specimen is performed by frozen-section examination, which can be analyzed immediately, and the results communicated to the operating room. Wedge resections, lobectomy, or pneumonectomy specimens are routinely evaluated intraoperatively to determine the status of the surgical resection margin; diagnose incidental nodules discovered at the time of surgery; and evaluate regional lymph nodes.

The postoperative evaluation includes examination of the surgical resection specimens related to lung cancer, which accounts for the largest proportion of current thoracic practice. The goal of pathologic analysis of surgical lung specimens is to classify the tumor type, provide information on staging and prognostic factors, such as the extent of tumor invasion, i.e., visceral pleural invasion (Fig. 67-1), venous/lymphatic vessel invasion (Fig. ...

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