76 Chapter 5 Figure 5. Images supporting the hypothesis of STAKS artifact. (continued) A, Autopsy lung showing bronchiolus with intraluminal fragment of cartilage. B through D, Pulmonary artery with intraluminal fragment of peripheral lung tissue and erythrocytes. E and F, Largely collapsed pulmonary vein with intraluminal foreign body material. G, Lung resected for adenocarcinoma with focally loose intraalveolar parts. H, Open lung biopsy for interstitial lung disease with intraalveolar fragment of loose benign bronchiolar epithelium (hematoxylin-eosin, original magnifications x2.5 [A], x1.25 [B], x10 [C, E, and G], x40 [F], and x20 [H]; cytokeratin 7, original magnification x10 [D]). An artificial model of an apple with ink clearly shows displaced ink in the direction of cutting (Figure 6, A through D). Since lung spaces are filled with paraffin during processing, the knife carryover within tissue holes is less likely to occur during microtome cutting, but may occur at the edge of the paraffin section (Figure 7, A). It is of paramount importance that the tissue floats are recognized as such and not considered separate foci of carcinoma in a lung tumor resection case. This may be challenging given the propensity for lung cancer cells to spread through vascular spaces or ‘‘presumed aerogenous spread.’’ Possibly, at least a part of the STAKS effect can be avoided by quickly cleaning the knife blade after each slice with a wet sponge or tissue paper.
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