A pathologist experienced in thoracic oncology is an essential member of the thoracic team. Surgical resection related to lung cancer and other pulmonary pathology accounts for the largest proportion of current thoracic practice. The goals of pathologic analysis of surgical lung specimens are to classify the lung cancer, determine the extent of its invasion (i.e., pleural, lymphovascular, soft tissue, or chest wall), and establish the status of the surgical margins for cancer involvement.1 Accurate disease identification and staging are of pinnacle importance to the decision-making process and influence the diagnosis (benign or malignant), course of treatment, selection of optimal surgical approach, and pursuit of appropriate adjuvant and neoadjuvant therapies such as chemotherapy, radiation, and other innovative approaches to treatment.
After a malignancy has been identified, the pathologist must determine whether the tumor is primary versus metastatic. Most tumors found in the lung represent metastatic foci from distant primaries, such as breast and colon cancer, as opposed to a primary lung malignancy. While the pathologic features of metastatic versus primary adenocarcinoma may be similar, for example, the treatment course is not. Immunohistochemistry is required to make the distinction and has proved to be an invaluable diagnostic adjunct. Primary malignant tumors of the lung are most often of epithelial or mesenchymal origin. The epithelial tumors are broadly divided into small cell lung cancer (SCLC) and non–small cell lung cancer (NSCLC). NSCLC is further classified as squamous cell carcinoma, adenocarcinoma, and large cell carcinoma (LCC).2
The pathologist plays a fundamental role in the preoperative, intraoperative, and postoperative evaluation. The preoperative evaluation includes examination of one of the following specimens: bronchial brushings, bronchial washings, fine-needle aspiration biopsy, core needle biopsy, endobronchial biopsy, and transbronchial biopsy. Because lung tumors demonstrate a great deal of heterogeneity, accurate classification depends on sampling technique: If the pathology sample is limited, sometimes the only categorization that can be made is the distinction between NSCLC and SCLC. Lymph node status is one of the most important prognostic features in patients with NSCLC.3,4 Since mediastinoscopy with pathologic examination of lymph nodes remains the “gold standard” for the evaluation of lymph node status in patients with NSCLC, mediastinal lymph nodes are sampled during the preoperative evaluation and provide information important to staging and therapeutic options.5–8
The intraoperative evaluation of the surgical pathology specimen is performed by frozen-section examination, which can be analyzed immediately, and findings are communicated to the operating room. Lobectomy or pneumonectomy specimens are routinely evaluated intraoperatively to determine the status of the surgical resection margin, to diagnose incidental nodules discovered at the time of surgery, and to evaluate regional lymph nodes.
The postoperative evaluation reveals pathologic characteristics necessary for classification of tumor type, staging, and prognostic factors. The parameters considered in the surgical pathology report are histologic type, histopathologic grade, visceral pleural invasion (Fig. 9-1), venous/lymphatic vessel invasion (Fig. 9-2), and extracapsular extension of ...