Anatomical Structure of the Pleura and Mesothelial Cells: What Are the Characteristic Features?

Abstract

It is important to understand the anatomy of the visceral and parietal pleura for an accurate pathological diagnosis of malignant mesothelioma. Elastic stains are helpful in understanding the microscopic anatomy of the pleura. Although there is controversy regarding the anatomy of the visceral pleura, it is believed to comprise five layers: mesothelial, submesothelial, external elastic, interstitial, and internal elastic. The submesothelial layer contains capillaries and lymphatic vessels in disease conditions, and the mesothelioma cells proliferate in this layer at an early stage. The interstitial layer is rich in capillaries and lymph vessels and is the plane of cleavage for pleurectomy/decortication. Some of the elastic fibers in the internal elastic layer are continuous with those in the alveolar wall. The anatomy of the parietal pleura is not fully clear. It is believed to comprise five layers: mesothelial, submesothelial, internal elastic, fibroadipose, and external elastic. The distance between the mesothelial and external elastic layers is variable and increases when fibrosis of the fibroadipose layer occurs. When extrapulmonary pneumonectomy is performed, the plane of the external elastic layer is dissected. Fat tissue, endothoracic fascia, striated muscles, and ribs are present outside the external elastic layer. Bundles of elastic fibers connect the parietal pleura and periosteum. The endothoracic fascia and external elastic layer of the parietal pleura are continuous from the thoracic wall to the peritoneal wall. The internal elastic layer in the thoracic wall runs in the direction of the diaphragm at the costophrenic angle.