Push pin induced artifact: A mimic of iron pill injury in gastrointestinal pathology

Dissection push pins (PP) are commonly used during formalin fixation to secure gastrointestinal (GI) resection specimens, allowing proper specimen fixation. We have observed iron diffusion from the PPs into the tissues that results in an artifact that can be confused with iron deposition described with iron pill associated mucosal injury and gastric glandular siderosis. We sought to characterize this tissue artifact in GI resection specimens.

Sections from 20 GI specimens (colon 11, small intestine 5, stomach 3, esophagus 1) were obtained from areas where PPs were applied after 24 (n = 15) and 48 (n = 5) hours of fixation. One control section from an area distant from the PP was also taken in each case. Prussian blue stain was performed on all sections and the pattern of iron deposition, diameter of diffusion, and any associated histologic changes were documented. Clinical charts and final diagnosis in each case was reviewed, and history of any iron supplementation was noted. Five cases each of iron pill associated gastritis and gastric glandular siderosis were included for comparison.

Fourteen cases (14/20; 70%) exhibited iron deposition where PP were applied (8 large intestine, 3 small intestine, 2 stomach, 1 esophagus) of which 7 showed crystalline green to black iron deposits along the mucosal surface and/or within the lamina propria and a fine and diffuse deposition throughout the wall was observed in twelve cases. This was seen largely as a circular ring-like area centered around the area of PP insertion and was easily evident on H&E stains but was better highlighted with Prussian blue stain. The maximum diameter of iron diffusion was 6.5 mm, with a median of 1.5 mm (IQR = 0-5), and the diameter seemed to increase with longer fixation, but this was not statistically significant. The fine granular staining was not confined to any specific cell type or layer of the bowel wall and involved epithelial and stromal tissues. There was no evidence of mucosal injury and none of the patients were on iron supplements. The control sections in each case lacked evidence of any iron deposition. The pattern of the PP associated iron deposition was compared with iron pill associated mucosal injury and gastric glandular siderosis and key differences were noted.

PPs can result in artificial iron deposition with crystalline and granular deposits that shows some morphologic overlap with iron pill (IP) induced mucosal injury. However, the circular pattern of deposition, absence of inflammatory response and lack of any cell or tissue specificity helps to distinguish it from iron pill induced injury or gastric glandular siderosis. Pathologists need to be aware of PP iron deposition artifact to differentiate it from other diagnoses with clinical relevance.