67 Artifacts and histologic pitfalls in the lung Introduction Normal lung histology including usual tissue artifacts is well described89. Unfortunately, virtually all writings and images are concerned with ‘‘static’’ morphologic findings. Recently, attention has been focused on dynamic changes in the lung that cause a pitfall in the diagnosis of pulmonary papillary adenocarcinoma90. It is certain that when one concentrates on a specific problem, one may not notice other, perhaps peripheral, issues. This ‘‘inattentional blindness’’ can occur in the interpretation of lung biopsies, especially when the pathologist focuses only on a particular aspect of a tissue sample and in doing so neglects other findings or even the possibility that the morphology has been altered by artifact(s)91. Ex vivo artifacts in lung samples have not been systematically investigated and it is useful to describe in detail possible mechanisms associated with several obvious changes. During the dynamic process of pulmonary resection and tissue handling several ex vivo artifacts occur, which have an impact on the histologic appearance of the lung tissue. The aim of this study is to describe and illustrate 4 mechanisms of ex vivo artifacts, namely, ‘‘surgical collapse,’’ ‘‘ex vivo contraction,’’ ‘‘clamping edema,’’ and ‘‘spreading through a knife surface.’’ These 4 mechanisms individually or in combination manifest with morphologic patterns that may lead to diagnostic pitfalls. Mechanisms of ex vivo artifacts Surgical Collapse The lung is usually deflated during segmentectomy, lobectomy, and pneumonectomy, causing so-called surgical atelectasis or collapse (Figure 1A). Deflation of the surgical lung is achieved by double-lumen endotracheal intubation, allowing selective ventilation of the nonsurgical lung92, 93. Surgical collapse also affects the pulmonary vasculature with emptying of the blood and lymph vessels. During removal of the lung, the physiologic negative pressure between the visceral and parietal pleura is replaced by atmospheric pressure, leading to additional compression of the removed lung tissue. Manual pressure applied by the surgeon(s) may also contribute. Thus, surgical collapse encompasses 3 components. In the time frame of inspiration and expiration, approximately 3 to 4 seconds, 250 ml of air flows in and out of each lung. Interestingly, the deflation process during surgery takes longer. This is in part due to the ‘‘columns’’ of lymph in the superficial and deep lymphatic vessels. Emptying of the lymph into the draining lymph nodes is a slower process (minutes) compared to inspiration and expiration. Importantly, during this process of surgical collapse not all lung parts may collapse in a similar manner. If, in addition to the abovementioned 3 aspects, adenocarcinoma in situ or atypical adenomatous hyperplasia is present, then the alveolar walls are more rigid. This reduction in compliance causes a slight reduction in lung collapse, compared 5
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