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A 60-year-old woman with systemic lupus erythematosus, diabetes mellitus and chronic kidney disease presented to the respiratory clinic for shortness of breath on exertion for 6 months and an abnormal routine chest radiography obtained 1 year earlier. She did not have cough, sputum or chest pain. On examination, she was alert and oriented without distress. Auscultation revealed bilateral expiratory wheezes and normal heart sounds without murmur. Her oxygenation was 96% while she was breathing ambient air. Chest radiograph (figure 1A) and CT of the chest (figure 1B) showed bilateral, multiple, variable-sized pulmonary nodules and masses. The lesions were round or polygonal in shape, non-enhancing after contrast injection, with right lower lobe predominance (figure 1C). She had been told that a routine chest radiography 1 year earlier showed multiple pulmonary nodules. Pulmonary function test revealed moderate obstructive ventilator defect with moderate impairment of diffusion capacity. She underwent thoracoscopic wedge resection of the right upper and middle lung for tissue proof for the presumed diagnosis of primary lung cancer with lung metastases. Histology examination showed granulomas with central hyalinised collagen arranged in whorls (figure 2A), with surrounded plasma cells and lymphocytes infiltrates between collagenous bands (figure 2B). The bundles of hyalinised fibres were stained blue in Masson’s trichrome stain (figure 2C). A diagnosis of pulmonary hyalinising granuloma (PHG) associated with underlying autoimmune disease was made. She was treated sequentially with azathioprine, cyclophosphamide and mycophenolate mofetil, in addition to baseline oral prednisolone. Pulmonary function test 3 years after treatment revealed mild obstructive ventilator defect with normal diffusion capacity. Chest radiography 5 years after treatment showed stationary multiple pulmonary nodules and masses with prominent calcifications (figure 1D).
PHG is a rare benign pulmonary condition that was first described by Engleman et al in 1977,1 with less than 150 patients reported between 1964 and 2015.2 The aetiology and pathogenesis of PHG remain unknown, but are postulated to be associated with an abnormal immune response to a variety of infectious, autoimmune or haematological diseases. The most frequent radiographic finding is bilateral, multiple, randomly distributed nodules or masses that rarely calcify or cavitate.3 The calcification may represent a late radiographic consequence, as in this case. Due to a close resemblance to primary or metastatic lung cancer, the histological diagnosis is inevitably warranted, which typically shows homogeneous hyalinised collagen, with surrounded plasma cells, lymphocytes and histiocytes. The diagnosis could be established by CT-guided percutaneous biopsy or surgical resection, while bronchoscopic biopsy has not yet been reported to achieve diagnosis.3 Positron emission tomography (PET)-CT may not be a useful tool to differentiate PHG from malignant pulmonary nodules. The literature review shows that 60% of patients with PHG had hypermetabolic pulmonary lesions on PET-CT scan, with standard uptake variation ranging from 2.2 to 9.6.2 There is no evidence-based strategy to inform therapy. While patients may not be improving radiographically, the prognosis is often favourable. Although rare, PHG is a disease that ought to be included in the differential diagnosis of patients presenting with multiple pulmonary nodules or masses.
The authors thank Ms Chien-Ching Hung for performing Masson's trichrome stain. She is affiliated with the Department of Pathology, National Taiwan University Hospital Hsin-Chu Branch, Hsinchu, Taiwan.
Contributors L-TK and W-YL: drafting the manuscript. H-NH and H-JK: image preparation. S-KL: revising the manuscript.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
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