Bronchial Anthracofibrosis (2013)

To the Editor: In general, a large lung mass seen on a computed tomography (CT) scan of the chest is considered malignant until proven otherwise, especially in those with high risk. Differential diagnosis of a lung mass includes neoplastic (malignant or benign) and non-neoplastic causes. Infections such as tuberculosis, fungal, or parasitic infections are considered in the endemic areas once neoplasm is excluded. Here, we report a case of bronchial anthracofibrosis (BAF) that presented with a large lung mass. BAF is not routinely included in the differential diagnosis of a lung mass, at least in the United States. Although imaging studies and bronchoscopic airway examination provide clues toward the diagnosis, a definitive diagnosis is made by bronchoscopic biopsies. A thorough search for malignancy and underlying tuberculosis infection is necessary. A 66-year-old man was referred for evaluation of a right parahilar mass that was found incidentally when he presented to the emergency department with neck pain after a physical work in his yard. Imaging studies revealed multiple focal lucencies in cervical vertebral bodies on a cervical CT scan, reported as suggestive for bony metastases, and a large parahilar mass measuring 5.4×5.3 cm in diameter, obstructing the right middle lobe (RML) bronchus, distal to the bifurcation of the bronchus intermedius and extending superiorly involving the apical and anterior segmental right upper lobe (RUL) bronchi. There was also an atelectatic collapse of the RML and innumerable pulmonary nodules in the right lung, raising the possibility of metastatic disease on CT chest (Fig. 1). The patient was diagnosed with chronic obstructive pulmonary disease several years ago and underwent a bronchoscopy with biopsies for a lung lesion in 2010 in Pakistan. He was told that he did not have malignancy and was treated with several inhalers for his chronic obstructive pulmonary disease. He also remembered having several bouts of pneumonia that were treated as outpatient during past 2 years. He also complained of long-standing cough with dark colored phlegm production and dyspnea on exertion. He had a history of chewing tobacco and working as a truck driver. He denied weight loss, fever, or tuberculosis exposure, but he had never been tested for the latter condition. The only abnormal laboratory studies were mildly elevated C-reactive protein and positive QuantiFERON-TB Gold test. The patient underwent flexible bronchoscopy and endobronchial ultrasound-guided biopsies with high clinical suspicion of primary lung cancer. Airway examination revealed areas of discoloration in the right main bronchus and 90% obstruction of RML bronchus without an endobronchial mass and black discoloration on the bronchial mucosa (Fig. 2). Needle aspirations and endobronchial biopsies revealed necrotizing granulomatous inflammation with negative staining for fungi and mycobacteria. Seven days later, flexible bronchoscopy was repeated to obtain more biopsies for pathologic and microbiological evaluation. Biopsies from the mucosal discoloration and lung parenchyma confirmed anthracotic pigmentations and chronic inflammatory changes confirming diagnosis of BAF. Transbronchial biopsies from the RML and RUL and bronchioalveolar lavage (BAL) from RML were sent for microbiological staining and cultures. BAL fluid cultures came back positive for Mycobacterium tuberculosis complex by DNA probe, and the patient was started on 4-drug regimen treatment. Magnetic resonance imaging of the spine with contrast showed hemangiomas as explanation of lucencies seen on the CT scan.FIGURE 1: A, Computed tomography (CT) scan of the chest showing the right parahilar mass. B, CT scan of the chest showing multiple nodular densities in the right upper lobe.FIGURE 2: Bronchoscopic image showing anthracotic mucosal discoloration.BAF usually presents as bronchial narrowing or obliteration caused by a mass with black (anthracotic) pigmentation of the overlying mucosa.1 BAF is not an uncommon condition and is well described in Asia where air pollution is prevalent. It is very rare in developed countries.2–4 The majority of the patients are female.5 As in our patient, the patients may have cough, dyspnea, or chest pain.6,7 Imaging findings of BAF are nonspecific and difficult to differentiate from bronchogenic carcinoma and tuberculosis.2 Atelectasis distal to bronchial narrowing as well as calcified and noncalcified mediastinal and hilar lymphadenopathy have been described as CT findings. Also reported are parenchymal abnormalities, such as consolidation, interstitial infiltration, and mass lesions.6 One distinguishing feature about bronchial narrowing in BAF is multifocal and often bilateral (segmental or lobar) bronchial narrowing.2 Given the overlaps in imaging features of BAF with endobronchial tuberculosis and bronchogenic carcinoma diagnosis can only be finalized based on bronchoscopic and pathologic findings. Our patient, however, did not have any lymph node involvement, but there was an obstruction of the RML bronchus based on the CT scan findings. The right parahilar mass with pleural involvement seen in our patient is also observed in a large Korean study.5,6 Kim and colleagues described anthracosis of the bronchial mucosa as the most common bronchoscopic finding in the RUL (90.7%) followed by the left upper lobe (86.8%) and RML (68.8%) in their patients. Anthracosis refers to the presence of carbon particles in the lungs, not a disorder per se. Anthracosis is seen particularly in those who smoke or live in polluted cities or industrial environments. Our patient, although not a smoker, had a significant exposure to fuel smoke as a truck driver. His bronchoscopic examination was similar to those described in the literature and showed obstruction of the RML bronchus due to an extrinsic compression and anthracotic mucosal changes. Bronchial narrowing per se is more frequently observed in the RML (68.8%) followed by the RUL (64%) and most commonly multifocal (69.1%) without any obvious endobronchial lesions.6 The multifocal nature of bronchial narrowing favors BAF but does not exclude the possibility of malignancy.1 BAL of our patient was negative for acid-fast bacilli on staining but positive for M. tuberculosis on polymerase chain reaction. BAF is frequently associated with tuberculosis infection.1,6 Some authorities have even suggested that tuberculosis is the cause of BAF.1,5,6 It is suggested that the anthracotic pigments in the bronchial wall might be derived from anthracotic material from the affected adjacent lymph nodes. The lymph nodes involved by tuberculosis may perforate into the adjacent bronchi and carbon particles from the lymph nodes reach to the mucosa. Then, healing of the mucosa results in fibrosis and bronchial narrowing. Inhaled anthracotic particles themselves cannot induce focal bronchial abnormality leading to fibrosis. However, 40% to 70% of the patients did not have any evidence of tuberculosis. Another possible explanation is that an injured bronchial mucosa can lead to accumulation of anthracotic pigments from air pollutants or smoke and might subsequently undergo healing and fibrosis resulting in BAF. The compromised local immune system facilitates acid-fast bacilli to implant in the bronchial mucosa. Treatment of tuberculosis in a patient with BAF may lead to reversal of the airway narrowing.8 It is important to be aware of BAF and consider it in the differential diagnosis of a lung mass especially in those who smoke cigarettes and are immigrants from tuberculosis endemic countries.9 We also strongly suggest a thorough work up for underlying tuberculosis infection. Spyridon Fortis, MD* Tadashi Allen, MD† Reza Talaie, MD† H. Erhan Dincer, MD* *Department of Medicine, Division of Pulmonary, Allergy, Critical Care and Sleep Medicine †Department of Diagnostic Radiology, University of Minnesota, Minneapolis, MN