78 - Rare Primary Lung Tumors

Abstract

Rare pulmonary tumors are defined as malignancies of the lung parenchyma with low prevalence and unusual histology, that is, different from bronchogenic carcinomas—small and non–small cell lung carcinomas. Rare molecular subsets of non–small cell lung carcinomas, such as ROS1-, RET-, and NTRK-rearranged tumors, are then excluded from the definition, which is mostly based on histologic classification. In this setting, rare pulmonary tumors account for less than 1% of all primary lung tumors, whereas they correspond to more than 100 different histologic, molecular, clinical, radiologic, and prognostic entities. Pseudotumors have historically referred to any pseudoneoplasm but are now restricted to a specific heterogeneous group of diseases characterized by circumscribed fibrous tissue associated with inflammatory and myofibroblastic cells. The most frequent rare malignant primary lung tumors are—in decreasing order of frequency—carcinoid, mucosa-associated lymphoid tissue (MALT) lymphoma, and sarcomatoid carcinomas. Sophisticated pathologic and molecular analyses studies have an increasingly critical role in diagnosis and in therapeutics. High-throughput sequencing is recommended. The management of patients with rare pulmonary tumors requires continuous multidisciplinary expertise at each step of the disease. Dedicated networks are required to ensure high quality of care and may provide an infrastructure for collaboration with diagnosis and treatment.