LAUSR

IgG4-related disease (IgG4-RD) is an uncommon systemic disorder characterized by sclerosing lesions that can affect almost any anatomical site.1 Pulmonary involvement has highly variable clinical and radiological presentations.2 Although IgG4-related lung disease is usually preceded or accompanied by multi-organ involvement,3 rare cases of solely lung involving IgG4-RD have been described.4–6 Herein, we report two biopsy-proven cases of IgG4-RD with lung mass as the sole radiographic presentation. 64-Year-old man with a 27 mm spiculated mass in the right upper lobe on computed tomography (CT) in the setting of chronic cough with hemoptoic sputum. He was a previous smoker (100 pack-year of smoking). Bronchoscopy showed neither signs of bleeding nor morphological anomalies and bronchoalveolar lavage (BAL) was negative for malignant cells and acid-fast bacilli. Further investigation with positron emission tomography (PET) demonstrated a right upper lobe nodule with standardized uptake value (SUV) max of 2.6. Due to the high suspicion of primary lung malignancy, biopsy of the nodule was performed by transthoracic needle aspiration (TTNA), documenting a fibrocollagenous lesion with lymphoplasmacytic infiltration and wall thickening of venous-type vessels. On immunohistochemistry, the number of IgG4-positive plasma cells was >20 per high power field (HPF) and immunostaining for CD20 and CD3 was positive. The serum concentrations of total IgG and IgG4 were normal. 71-Year-old man who presented with posterior upper thoracic pain for 2 years. He is an active smoker with 50 pack-year of smoking. Chest CT detected a 35 mm spiculated mass in the right upper lobe, which was biopsied by TTNA. Histological examination demonstrated a nodular lesion with total architectural distortion due to fibrosis and lymphoplasmacytic infiltration. On immunohistochemistry, the number of IgG4-positive plasma cells was >30 per HPF. Given the suspicion of IgG4-RD further workup was