In this study, we examined pathological characteristics of the bronchial glands collected by TBLC. Our results showed that high-grade lymphocytic infiltration in bronchial glands was a distinct characteristics in SS, although mild lymphocytes infiltrations in bronchial glands were occasionally observed in other collagen diseases or other interstitial lung diseases.
SS is characterized by B-cell hyperactivity and lymphocytic infiltration of exocrine glands and other target organs. The pulmonary manifestations of SS are xerotrachea, airway abnormalities, interstitial pneumonia, and lymphoproliferative disorders [18-23]. Xerotrachea is associated with lymphocytic inflammation and atrophy of the submucosal gland . There is only one literature that reported on a case that transbronchial forceps biopsy specimen showed a dense infiltrate of lymphocytes around the bronchial gland in SS patient, despite that the collected bronchial gland was small . Others reported that the bronchial glands in SS showed significant hyperplasia, without mentioning the inflammatory cells in the bronchial glands . As they studied on the autopsy lungs, their subjects may have been affected by treatment such as steroids and immunosuppressant.
SS has characteristic microscopic findings involving lymphocytic infiltration surrounding the excretory ducts in combination with the destruction of acinar tissue. In early stage or advanced phase of SS, there is often slight or none lymphocyte infiltration in the salivary glands. Dilatation of intralobular and interlobular duct is a common finding in the salivary glands of SS, regardless of the degree of lymphocyte infiltration . In this study, duct dilatation in the bronchial glands was observed only in SS. Because this study was a small and retrospective study, we could not compare the degree of respiratory symptoms such as cough with the degree of lymphocytic infiltration of the bronchial glands. In patients with Sjögren's syndrome who complain of severe persistent cough despite mild or no interstitial pneumonia, exocrine dysfunction of the bronchial glands may be involved, and a bronchial gland biopsy may prove this. Comparing the degree of lymphocytic infiltration of the bronchial glands with clinical symptoms such as cough is future work.
Cryobiopsy is a new technique for diagnosing diffuse parenchymal lung disease [4-7]. TBLC provides larger samples than transbronchial forceps biopsy and more proximal portion of the lung apart from the pleura than SLB. A bronchial gland is rarely biopsied by SLB for diagnosing interstitial lung disease. In previous reports on bronchial glands, the specimens were obtained by autopsy or lung resection for localized pulmonary lesions [26,28]. Autopsied lungs are affected by treatment during their lifetime. There was no report that examined lymphocytes infiltration in bronchial glands of collagen diseases or interstitial lung diseases by lung resection. As we excluded the cases that had been treated before biopsy, the cases of this study were not affected by treatment such as steroids or immunosuppressant. The present study is the first report focusing on lymphocytes infiltration in the bronchial glands with various interstitial lung diseases that were not affected by treatment. Complications of bleeding in the specimens including bronchial glands were not more common than previous reports, and there was no severe bleeding .
This study has several limitations. First, this was a small, retrospective study, which may have been subject to various biases. Second, bronchial glands were incidentally biopsied in this study. As we performed TBLC for the diagnosis of diffuse lung diseases, we did not intend to biopsy bronchial glands. Bronchial glands are present in trachea and bronchus with cartilage. If we evaluate focus on lymphocytes infiltration in bronchial glands, transbronchial biopsy in the central airway should be considered. Third, an adequate sample size to evaluate lymphocyte infiltration of bronchial glands is unknown. Because lymphocytes infiltration in salivary glands of SS have irregular distribution, a sufficient volume of specimen is needed in salivary gland biopsy. If a sample is small, the degree of lymphocytes infiltration may be misinterpreted. In this study, we examined the cases that had sufficient size of bronchial glands. We excluded the cases with small size of bronchial glands (< 0.05mm2), although it is necessary to examine whether this criteria is appropriate in the future. Finally, we were not able to compare the degrees of lymphocytic infiltration in the salivary glands and the bronchial glands of SS and did not evaluate SS patients without interstitial pneumonia.