Correct!
2. Fibrosing mediastinitis
Inflammatory myofibroblastic tumor can result in abnormal mediastinal and/or peribronchial soft tissue that calcifies and produces mass effect, including vascular and bronchial narrowing, but the process is more likely to be focal rather than multicentric and bilateral. Sarcoidosis remains a possibility, but the appearance of the calcification and associated mass effect, as well as the absence of the typical parenchymal features of this disorder, suggest that sarcoidosis is less likely than fibrosing mediastinitis. Metastatic malignancy is also unlikely, given the presence of calcification within the abnormal peribronchial soft tissue and the absence of both lung nodules and a history of a calcifying or ossifying extrathoracic primary malignancy. Congenital interruption of the pulmonary artery could account for the small left pulmonary arterial system and the associated bronchial artery hypertrophy, but typically this process occurs on the side opposite the aortic arch (this patient’s aortic arch is left-sided, so the interruption would be present on the same side of the aortic arch), and interruption of the pulmonary artery would not account for the right-sided abnormalities or the calcified soft tissue.
Diagnosis: Fibrosing mediastinitis, due to Histoplasma capsulatum
The patient was diagnosed with fibrosing mediastinitis and did well without intervention for a number of years. A slight decrease in her vital capacity was noted over an 11-year period since her diagnosis, perhaps with slight progression in exercise-induced dyspnea. Subsequently, she then presented with some worsening dyspnea, which prompted chest radiography (Figure 6), which showed worsening right lower lobe opacity and increasing volume loss.
Figure 6: Frontal (A) and lateral (B) chest radiography shows worsening of right lower lobe opacity with right lung volume loss. A new small right pleural effusion is also present.
These abnormal results prompted repeat thoracic CT (Figure 7), which showed worsening atelectasis in the right lower lobe due to right lower lobe bronchial obstruction.
Figure 7. Representative images form axial unenhanced CT displayed in soft tissue windows shows that the worsening right lower lobe opacity seen at chest radiography is due to obstruction of the right lower lobe bronchus (arrowhead), just distal to the origin of the superior segment right lower lobe bronchus (arrow), with associated atelectasis. The calcification of the peribronchial soft tissue bilaterally is well-appreciated with unenhanced technique.
Severe narrowing of the right lower lobe bronchus was confirmed with bronchoscopy (Figure 8); the left-sided airways were patent.
Figure 8. Severe narrowing of the right lower lobe bronchus.
No evidence of infection was noted on bronchoalveolar lavage. Despite the apparently worsening imaging findings, the patient’s pulmonary function testing results remain stable and she remains only minimally symptomatic with exercise.
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