Histopathologic evaluation of mediastinal lymph nodes in lung cancer.

Regional lymph nodes represent the most frequent metastatic site in lung cancer. During histopathologic assessment of lymph-node involvement, in the presence of gross tumour, one or several HEtE-stained sections will suffice to demonstrate the tumour and its possible extranodal extension. In the absence of macroscopically detectable metastatic tumour growth, the entire node should be submitted for microscopic examination and be cut into 3- to 4-mm slices in the longitudinal or transverse plane. If the node is sliced, care should be taken to process different surfaces for microscopic examination. After neoadjuvant therapy, the percentage of therapy-induced necrosis and the still vital tumour tissue in the dissected lymph nodes should be estimated microscopically. EUS-guided fine-needle aspiration with subsequent cytologic examination represents a complementary method in the evaluation of mediastinal lymph-node lesions. The proposed way of histopathologic evaluation of mediastinal lymph nodes tries to reach a high diagnostic yield, and to offer a compromise between theoretical demands and practical feasibility.