Cytologic features of benign solitary pulmonary nodules with radiologic correlation and diagnostic pitfalls: a report of six cases.

Background: The solitary pulmonary nodule (SPN) is a common radiologic abnormality often detected incidentally. The majority of SPNs represent benign processes, including granulotmatous inflammation, bronchogenic cysts and hamartomata. 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, hemartoma, 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.