Introduction

Of all the organs, lung is the most likely to have a false-positive cytologic diagnosis, because irritated type 2 pneumocytes can become markedly atypical with enlarged hyperchromatic nuclei and prominent nucleoli, mimicking adenocarcinoma. This chapter deals with benign lung tumors and non-infectious tumor-like lesions. In most hospitals, approximately 30% of the transthoracic fine needle aspiration (FNA) biopsies are benign. Some benign lesions, i.e., sarcoidosis, radiologically mimic malignancy, presenting as lung masses with hilar adenopathy. Positive positron emission tomography (PET scan) in a metastatic work-up can be alarming clinically. One needs to remember that a PET scan measures metabolic activity. Increased uptake can occur in metabolically active but benign lesions. Cytopathologists are sometimes under pressure from clinicians to overcall a lesion so the diagnosis matches clinical impression. One needs to remember that the truth lies in the cells and substances that are sampled from the lesion. Although bronchial brushes and transbronchial FNA are done by pulmonologists, the vast majority of the diagnostic cases in this author’s experience were obtained by radiologists using a percutaneous transthoracic approach.

PULMONARY HAMARTOMA

Clinical features

Pulmonary hamartomas account for about 75% of benign lung tumors. Grossly, the tumor is a sharply delineated and lobulated ovoid nodule, measuring up to 4 cm. It most commonly occurs in adults, usually men. It sometimes presents as an intrabronchial polypoid mass causing obstruction.