The histologic pattern of usual interstitial pneumonia is heterogeneous areas of interstitial inflammation, dense acellular collagen deposition, fibroblastic foci, and honeycombing . Various clinical conditions have been known to be associated with usual interstitial pneumonia, including idiopathic pulmonary fibrosis, collagen vascular disease, drug toxicity, chronic hypersensitivity pneumonitis, asbestosis, and infection with agents such as Epstein–Barr virus and HIV-1 [2–4]. To our knowledge, however, an association between usual interstitial pneumonia and chronic pulmonary ischemia has not been reported in the English literature. We present a case of unilateral usual interstitial pneumonia associated with slowly growing pulmonary artery sarcoma and suggest that chronic pulmonary ischemia may be one of the etiologic factors in usual interstitial pneumonia.
A 52-year-old man with dyspnea was admitted to our institution. The medical history revealed that he had been admitted to a local hospital 5 years previously because of the incidental finding of a pulmonary mass on a chest radiograph obtained for a routine medical examination. Contrast-enhanced chest CT pursuant to the chest radiograph showed a 5.5 × 2.5 cm intraluminal filling defect in the right main pulmonary artery, raising the possibility of pulmonary artery sarcoma (Fig. 1A). No other abnormality was present in the underlying lung parenchyma (Fig. 1B). Excisional biopsy of the intravascular mass was recommended, but the patient declined because he had no specific symptoms and feared major surgery.
Five years after the evaluation at the local hospital, the patient had gradually increasing dyspnea and was admitted to our institution for further evaluation. Contrast-enhanced chest CT showed the previously detected intravascular mass in the right main pulmonary artery had increased in extent, measuring 8.5 × 3 cm in maximum diameter and extended to the lobar branches of the pulmonary artery (Fig. 1C). The presence of several tortuous hypertrophied intercostal arteries newly identified in the right hemithorax and hypertrophy of the right bronchial artery suggested a systemic arterial supply to the ipsilateral right lung in association with chronic pulmonary ischemia (Fig. 1C). On lung window high-resolution CT scans (1-mm collimation), the ipsilateral right lung exhibited subpleural areas of ground-glass attenuation and irregular linear opacities with honeycombing, findings suggestive of usual interstitial pneumonia (Fig. 1D).
To confirm the diagnosis and for treatment, open thoracotomy and excisional biopsy were performed. At surgery, frozen biopsy specimens obtained from the right main pulmonary artery contained pulmonary artery sarcoma. The patient underwent curative right pneumonectomy and reconstruction of the main pulmonary artery with a bovine pericardial patch. Multiple collateral vessels were identified along the costal pleura. Gross examination revealed a pale yellowish partly myxoid intravascular mass in the lumen of the right main pulmonary artery (Fig. 1E). The tumor exhibited mainly intravascular polypoid growth with focal invasion of the adjacent lung parenchyma. Histopathologic examination of the intravascular mass revealed low-grade pulmonary artery sarcoma consisting of atypical spindle cells in myxoid stroma, moderate cellular pleomorphism, and rare mitoses. The biopsy specimens obtained from the subpleural lung parenchyma of the right middle and lower lobes contained areas of microscopic honeycombing and irregular interstitial fibrosis, findings consistent with usual interstitial pneumonia (Fig. 1F). The patient recovered uneventfully and had no evidence of local recurrence or distant metastasis 2 months after surgery.
The systemic arterial supply to the lungs can be congenital or acquired . Hypertrophy of normal systemic arteries, which include the bronchial arteries, intercostal arteries, internal mammary arteries, inferior phrenic arteries, and branches of the thyrocervical trunk, has been known to develop in patients with bronchiectasis, pulmonary tuberculosis, chronic pulmonary thromboembolism, or chronic obstructive pulmonary disease . These systemic arteries supply the lungs by means of intrapulmonary bronchopulmonary arterial anastomoses or transpleural systemic–pulmonary artery anastomoses .
In patients with chronic pulmonary thromboembolism, the reduction in pulmonary arterial pressure due to pulmonary artery occlusion is known to result in tortuous dilatation of bronchial arteries, which serve as collateral vessels supplying the ischemic lung . The systemic–pulmonary arterial communication also has been found in association with chronic pulmonary artery occlusion induced by Takayasu's arteritis . In our case, we believe that a very slowly growing low-grade pulmonary artery sarcoma had been causing longstanding pulmonary ischemia due to pulmonary arterial occlusion, which led to secondary hypertrophic changes in bronchial and intercostal arteries, making them collateral vessels for systemic arterial supply to the ischemic lung.
Usual interstitial pneumonia is a relatively nonspecific pattern of chronic lung injury characterized by fibrosis and honeycomb remodeling . Although various clinical conditions, including collagen vascular disease, drug toxicity, chronic hypersensitivity pneumonitis, asbestosis, and viral infection, have been known to be associated with usual interstitial pneumonia [2–4], the association with chronic pulmonary ischemia has not been not reported, to our knowledge. In our case, we believe that unilateral usual interstitial pneumonia might have been derived from 5 years of chronic ischemic lung injury induced by slowly growing pulmonary artery sarcoma. The presence of a chronic ischemic lung injury can be supported by compensatory hypertrophic changes in the ipsilateral bronchial and intercostal arteries, which served as collateral vessels for the ischemic lung. An alternative explanation for the unilateral pulmonary fibrosis is the possibility of the presence of a fibrogenetic factor secreted from the sarcoma, localizing with more concentration in the ipsilateral lung, and resulting in pulmonary fibrosis. The findings in our case of unilateral usual interstitial pneumonia associated with slowly growing pulmonary artery sarcoma suggest that chronic pulmonary ischemia may be an etiologic factor in usual interstitial pneumonia.
Address correspondence to T. S. Kim.
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