Elastosis is described as the focal excess of elastic fibers in the tissue. Elastosis has been commonly observed in the cardiology literature where it deposits as a fibroelastoma on cardiac valves associated with high risk of embolism and often needing surgery. It has also been reported in the gastrointestinal (GI) tract often presenting as a mouth lesion or a colon polyp and on the skin as a tumorous growth. Elastosis in the lungs is extremely rare. Till present, there has been only one case of bronchial elastosis published in a French paper. Hereby, to the best of our knowledge, we report the second rare case of bronchial elastosis presenting as right lower lobe (RLL) lung collapse.
An 89-year-old nonsmoker male with the past medical history of hypertension, dementia, and benign prostatic hyperplasia presented with progressive worsening of shortness of breath for 5 months and mild cough with clear white color sputum. He denied any fevers, chills, weight loss, night sweats, or loss of appetite. On physical examination, he was alert and oriented, with normal vital signs. His SpO2 was 92% while breathing ambient air. Bilateral diminished respiratory excursion and faint bibasilar wheezing were noted on chest examination, and cardiac auscultation found no murmurs or irregularities. The blood cell counts, electrolytes, and renal and liver function tests were unremarkable and QuantiFERON-Tuberculosis Gold was negative. An arterial blood gas analysis showed pH 7.45, PCO233.9 mmHg, and PO268.1 mmHg on room air. Chest radiography showed right-sided pleural effusion [Figure 1], and computed tomography of the chest showed bilateral pleural effusion right greater than left, with atelectasis of RLL [Figure 2]. The patient underwent diagnostic and therapeutic right-sided pigtail catheter placement which drained serous exudative pleural fluid on Light's criteria with lymphocytic predominance. Pleural cultures and cytology were negative. Postpleural fluid drainage and repeated chest imaging showed right-sided unexpandable lung with pneumothorax ex vacuo and possible endobronchial lesion in the right middle lobe (RML) bronchus [Figures 3 and 4]. Subsequently, bronchoscopy was performed which showed narrowed RML bronchi with significant mucosal edema and a round smooth-bordered 3.0 cm endobronchial lesion at RLL bronchi not allowing the bronchoscope to pass beyond the lesion. Endobronchial biopsies, bronchoalveolar lavage, and cytological brushing were performed. RML biopsy showed chronic bronchitis and was negative for malignancy or granulomatous inflammation. RLL biopsy with Verhoeff's elastic staining showed plexus of elastic fibers parallel to basement membrane [Figure 5]. Immunoperoxidase staining on RLL showed the presence of elastic tissue as fibrillar amphophilic material which was centered around blood capillary vessels consistent with the diagnosis of bronchial elastosis [Figure 6]. The first cytology from pleural fluid was negative, and because of the patient's wishes, no further staging and intervention including bronchoscopy removal or surgical resection were performed. After physiological and clinical improvement, the patient was discharged in a stable condition to a long-term care facility.
Endobronchial lesion can be malignant neoplasms, benign tumors, aspirated foreign bodies, postinflammatory, infectious, or traumatic strictures, and inflammatory polyps. Amyloidosis is one of the rare causes of endobronchial lesions. The most common are the primary malignancies including bronchogenic carcinoma and carcinoid tumors. Benign endobronchial tumors can be divided into tumors of mesenchymal, submucosal gland, and surface epithelial origin. Of these, tumors of mesenchymal origin represent the great majority, with the most common being hamartoma. Benign endobronchial neoplasms are a rare entity, and they may present with diverse pathological findings. Endobronchial tumors usually present with symptoms such as cough, hemoptysis, recurrent pneumonia, wheezing, and chest pain. However, bronchial elastosis, a benign tumor of mesenchymal origin, has only been reported once in French literature thus far.
The elastin content of lungs is quite variable, ranging from as low as 2% in rodents up to 28% in the cow and in humans. For this reason, most of the chemical and biological studies that have been conducted on elastin have used either the bovine neck ligament or the ascending aorta of several species. Elastic fibers are ubiquitous in the lung, associated with collagen and proteoglycans. Elastin and collagen fibers from alveoli, bronchi, interlobular septae, and the pleura all appear to have connections with fibers of pulmonary arteries. Elastic fibers in respiratory bronchioles become more distinct distally, where the alveoli are also more developed.
Arrigoni et al. studied 130 patients with benign tumors of the lung and only 6% of those were endobronchial in location. Elastosis can occur when loss of function mutations arise to genes responsible for elastin production. This leads to overproduction of elastic tissue. Elastic tissue overproduction can be seen as small, uniform, symmetric papules that vary in anatomic location. Histologic examination finds overproduction of elastic tissue in an interlaced or fragmented pattern. Elastosis is viewed as finely granular and/or fibrillar amphophilic material, which can sometimes include a fibrous component also known as elastofibromatous change. These changes appear centered around blood vessels as in our patient's pathology. The phenotypical appearance is often mistaken for amyloid, but Congo red stains remain negative whereas they stain strongly positive for elastin.
Elastosis has been reported in cardiology, GI, and dermal literature. In cardiac literature, the origin of these tumors is still in question whether they are congenital or acquired. Most are found on cardiac valves, and they are believed to be acquired by a microthrombi theory which entails small microthrombi coalescing on cardiac valves leading to endothelial damage and then forming elastomas. These elastomas have a tendency to become embolic. Histology from cardiac valve elastomas shows elastin and collagen fibers surrounded by endocardium. In GI literature, most elastomas are found incidentally during colonoscopy and sometimes present as small intestinal obstruction, abdominal pain, and/or hematochezia. The median age of presentation is in the seventh decade with equal male:female ratio. Pathology shows increased elastic fibers fine to fibrillary pattern and as bundles with angiocentricity. Etiology of these lesions in the GI system is unknown, but theories include reactive and degenerative processes including possible elastic degeneration of submucosal vessels and mucosal prolapse.
Endobronchial lesions are usually malignant but when benign the differential diagnosis consists of lipoma, hamartoma, neuroendocrine tumors, amyloidosis, etc. Amyloidosis is more heavily considered in the differential as pathology is difficult to differentiate based on hematoxylin and eosin stains alone. Special stains for elastin are needed as performed in the case of our patient. Flexible bronchoscopy is necessary for diagnosis and evaluation of these endobronchial tumors. Bronchoscopy removal or surgical resection is the modality of treatment for these tumors. Surgery is considered for patients with having lesions with increased risk of recurrence, extrabronchial extension of the lesions, or destruction of the peripheral lung due to long-term atelectasis.
In our case, the bronchial elastosis was found to be the rare cause of an endobronchial obstructive lesion resulting in an unexpandable lung. Patient's clinical symptoms improved temporarily by drainage of pleural effusion; however, the cause of the endobronchial lesion needs to be treated to prevent further episodes of deterioration.
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