Clinical diagnosis
Case 141
【Discussion】
There are different lymphatic drainage channels in parietal pleura and visceral pleura. Pleural fluid is produced from pleural membrane (composed of mesothelial cells) via systemic vessels and absorbed or drained into lymphatic channels via small pores (called stomata) of the parietal pleura. Lymphatic channels in parietal pleura drained into intercostal, internal mammary, posterior mediastinal and diaphragmatic nodes. In principle, lymphatic channel in visceral pleura does not drain into parietal space but drains into bronchopulmonary nodes, and thereafter, drains into right or left mediastinal nodes and eventually right or left subclavian vein (1).
Meanwhile, pulmonary lymphatic channel has two directions; Lymphatic channels present at deep pulmonary area directly drains into bronchopulmonary nodes while lymphatic channels present at superficial area drain into the visceral pleural lymphatic channels and thereafter into bronchopulmonary nodes (2).
It is well known that Asbestosis involves lower lobe and makes pleural plaque or pleural thickening often associated with calcification, while silicosis involves upper lobe and makes swollen hilar nodes often associated with egg-shell calcification. What brought this difference? Irrespective of asbestosis or silicosis, when particles bigger than 5μm are inhaled, they are discharged via bronchial villi and when particle less than 5μm are inhaled, they reach to alveolar space (3, 4). Macrophages make clearance of these tiny particles by engulfing and/or expectorated. However, when it is unable to make clearance of these particles due to massive and/or long term exposure, retaining tiny particles induces macrophages being killed or causing aggregative inflammation with assistance of leukocytes and fibrotic granulation nodule and with assistance of fibrocytes (3, 4).
Un-clearance silicon penetrates into the lymphatic channel and causes aggressive response, inducing swollen hilum nodes. Un-clearance asbestos penetrates into visceral lymphatic channel and pleural space. Pleural macrophages response to asbestos inducing fibrotic granulation with assistance with fibrocytes, leading to pleural plaque and pleural thickening. The difference between silicon and asbestos is dependent upon whether the presence or absence of potency of the particles in penetrating to pleural space (3-5). In our second case, he was making a life by treating heat brick made of silicon for decades, chest CT showed marked swollen hilum nodes with tiny calcification (Fig. 2), not contradictory with pulmonary silicosis.
In the first case with laboratory test revealing high value of IL-2 1590 U/mL, chest CT showed swollen hilar nodes and patchy shadow with air bronchogram in the marginal areas which are the specific imaging findings for pulmonary lymphoma (6, 7).
【Summary】
We present three cases with bilateral swollen pulmonary hilar nodes; pulmonary lymphoma, silicosis and sarcoidosis. It is borne in mind that pleural fluid is produced from pleural membrane and drained into lymphatic channels via small pores (called stomata) of the parietal pleura. Lymphatic channel in visceral pleura does not drain into parietal space but drains into bronchopulmonary nodes. Lymphatic channels at deep pulmonary area directly drains into bronchopulmonary nodes, while lymphatic channels present at superficial area drain into the visceral pleural lymphatic channels and thereafter into bronchopulmonary nodes. When particle less than 5μm are inhaled, they reach to alveolar space. Macrophages make clearance of these tiny particles by engulfing. However, when it is unable to make clearance of these particles, retaining tiny particles induces macrophages being killed or causing aggregative inflammation and fibrotic granulation nodule. The difference between silicon and asbestos is dependent upon whether the presence or absence of potency of the particles in penetrating to pleural space.
Swollen hilar nodes and patchy shadow with air bronchogram is the specific imaging findings for pulmonary lymphoma.
【References】
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2.Ellis H, et al. Thoracic Lungs: blood supply, lymphatic drainage and nerve supply. Anaesthesia & Intensive Care Medicine 2008; 9: 462-463.
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4.Dodson RF, et al. Characteristics of asbestos concen-tration in lung as compared to asbestos concentration in various levels of lymphnodes that collect drainage from the lung. Ultrastruct Pathol 2007;31(2):95-133.
5.Kim KI, Kim CW, Lee MK, et al. Imaging of occupational lung disease. Radiographics 2001;21(6):1371-91.
6.Berkman N, Breuer R, Kramer MR, Polliack A. Pulmonary involvement in lymphoma. Leuk Lymphoma 1996;20:229–237
7.Hare SS, et al. The radiological spectrum of pulmonary lymphoproliferative disease, Br J Radiol. 2012 ; 85: 848–864.
2019.4.3