Cytologic Features of Benign Solitary Pulmonary Nodules with Radiologic Correlation and Diagnostic Pitfalls

Background The solitary pulmonary nodule (SPN) is a common radiologic abnormality often detected incidentally. The majority of SPNs represent benign processes, including granulomatous inflammation, bronchogenic cysts and bamartomata. However, a solitary nodule may also potentially represent an early stage of lung cancer or a metastasis. Diagnostic procedures such as percutaneous fine needle aspiration biopsy can exclude malignancy in a majority of cases and may eliminate the need for more invasive surgical procedure. Correlation of the findings on the FNAB with radiologic features is helpful in establishing the benignity. Cases We report the cytologic features of 6 cases of benign SPN: exogenous lipid pneumonia, sclerosing hemangioma, bemartoma, bronchogenic cyst, fungal granuloma and solitary fibrous tumor. We provide radiologic correlation for each entity and discuss the diagnostic pitfalls. Conclusion Cytologically, lack of nuclear atypia with bland chromatin is useful in separating benign from malignant SPN. Radiologically, smaller lesions with smooth, well-defined margins and calcifications are more likely to be benign. Our cases illustrate the cytologic and immunohistochemical features that can help to make a more precise diagnosis. The identification of these features, when correlated with imaging findings, allows the cytopathologist to better approach the SPN.