DIAGNOSTIC STRATEGIES FOR MULTIPLE PULMONARY NODULES

Abstract

SESSION TITLE: Wednesday Medical Student/Resident Case Report Posters SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: 10/23/2019 09:45 AM - 10:45 AM INTRODUCTION: Multiple pulmonary nodules are often challenging in terms of their workup. Having non-invasive diagnostic methods to exclude benign lesions such as pulmonary hamartomas is desirable and useful in avoiding risky invasive procedures. We present a case highlighting the non-invasive approach which we believe is under recognized. CASE PRESENTATION: A 49 year-old-female with an extensive smoking history was referred for known pulmonary nodules. Chest CT showed multiple ground glass opacities (GGO) within peripheral parenchyma of the lungs [Figures 1-3]. Given the patients history of smoking and the presence of GGO, malignancy was considered. CT imaging was evaluated for intranodular calcification or fat. No calcifications were observed but given the measured fat density of -124 HU a diagnosis of pulmonary hamartomas was made. Comparison with CTs from 15-years prior confirmed the stability and benign nature of the nodules. DISCUSSION: Pulmonary hamartomas are the most common benign neoplasms of the lung, representing 75% of non-malignant lung tumors. Most hamartomas are asymptomatic and are incidentally found on imaging within the peripheral parenchyma, however 10% are endobronchial. They are relatively stable with a volume doubling time over 400 days. Malignant transformation is rare thus observation is safe. However, studies have found an association with primary lung cancer. While typically solitary, pulmonary hamartomas have been observed in multiples, with one study showing an incidence of 3%. Extrapulmonary involvement, especially mucocutaneous and gastrointestinal locations, indicates Cowden disease. Characteristically, pulmonary hamartomas contain fat and/or “popcorn” calcifications, found in 60% and 5-50% of nodules respectively. Fat can be identified on CT with a Hounsfield values of -40 to -120 HU, and when found with smooth, sharply marginated nodules it provides a confident diagnosis of hamartoma. MRI is a less common imaging modality, but chemical-shift MRI shows potential in identifying intracellular lipid when CT is negative for intranodular fat. Additionally, CT texture mapping shows promise in classifying nodules via heterogeneity, something ordinarily reserved to histopathology of biopsied specimens. Lastly, PET-CT is available for characterizing intermediate to large pulmonary nodules, but increased FDG avidity of hamartomas can lead to misdiagnosis. CONCLUSIONS: Multiple pulmonary hamartomas can be diagnosed on chest CT by measuring fat density within nodules. Thin section CT is essential to avoid missing small foci of fat. When inconclusive, other imaging modalities such as chemical-shift MRI and CT texture mapping should be considered before invasive biopsy or PET-CT. Reference #1: Provenzale, James M., Rendon C. Nelson, and Emily N. Vinson, eds. Duke radiology case review: imaging, differential diagnosis, and discussion. Lippincott Williams & Wilkins; 2011. Reference #2: “Primary Lung Tumors Other than Bronchogenic Carcinoma: Benign and Malignant.” Grippi MA et al. Fishman's Pulmonary Diseases and Disorders, Fifth Edition. New York: McGraw-Hill; 2015. Reference #3: Ekinci, G. H., et al. "The frequency of lung cancer in patients with pulmonary hamartomas: An evaluation of clinical, radiological, and pathological features and follow-up data of 96 patients with pulmonary hamartomas.” Revista Portuguesa de Pneumologia (English Edition) 2017; 23(5): 280-286. DISCLOSURES: No relevant relationships by jayanth keshavamurthy, source=Web Response No relevant relationships by Matthew Potter, source=Web Response No relevant relationships by Varsha Taskar, source=Web Response No relevant relationships by Thomas Whitton, source=Web Response