Key Points

• A number of tumor types straddle the line between benign and malignant, or, although generally benign, they may rarely behave in a malignant fashion.
• Only specific patterns of calcification or presence of fat density on CT are reliable radiographic indicators of benignity; PET scan provides further diagnostic assistance.
• Parenchymal lesions that remain indeterminate after radiography require careful short-term follow-up or tissue diagnosis generally obtained by needle biopsy or thoracoscopic excision.
• Benign endobronchial lesions can be resected bronchoscopically, but such resections are often incomplete; therefore, the patients need to be followed closely, and parenchyma-sparing sleeve resections need to be considered for recurrence.

Most benign tumors of the lung are rare neoplasms. Although many of these lesions manifest as solitary pulmonary nodules, and occasionally as multiple nodules, slightly less than 15% of such nodules are benign.[1] The classification of benign tumors (Box 1) remains somewhat controversial because of disagreement regarding the origin and prognosis of some of the more common lesions. A modification of the classification proposed originally by Liebow [2] seems to be the simplest and most elegant scheme and serves our purposes well, although one could also use the 2015 WHO classification.

The Liebow classification organizes lesions according to their presumed origin, whether epithelial or mesodermal. A number of the lesions, however, must be classified as unknown in origin and some as inflammatory. Electron microscopy provides more accurate detail than does light microscopy with regard to ultrastructure. The availability of this technique led to a revision in the classification of several lesions that were previously thought to be benign. Intravascular bronchoalveolar tumor, also known as sclerosing hemangioendothelioma, and pulmonary blastoma were both considered to be benign but now are known to behave in a malignant fashion. Solitary fibrous tumor is a tumor that straddles the line between benign and malignant. The names themselves imply the benign nature originally attributed to these tumors. The current understanding of atypical adenomatous hyperplasia, which appears to represent a premalignant lesion, is slightly more complex and is discussed later.

This chapter discusses the presentation, diagnosis, pathology, and management of the benign neoplasms encountered in the lung and focuses in particular on the influence that thoracoscopic excision plays, now that it is firmly established in the armamentarium of the general thoracic surgeon.