Intercellular adhesion molecule 1/2 and E-selectin in plasma cell mastitis: immunohistochemical study of 35 cases

Plasma cell mastitis (PCM) is one of the most frequently encountered inflammatory diseases of the nonlactating breast. Histologically, PCM is characterized by infiltration of relatively abundant plasma cells into the mammary ducts. Its pathogenesis has remained unknown. In this study, we immunolocalized intercellular adhesion molecule (ICAM) 1 and 2 and E-selectin, all of which play pivotal roles in the inflammatory process, in 35 cases of PCM. We then compared the results with those of non-PCM and nonpathologic breast tissue. In the ductal epithelium, ICAM-1 immunoreactivity was significantly more pronounced in PCM than in non-PCM (P = .045). Both ICAM-1 (P < .001) and ICAM-2 (P = .001) were significantly more pronounced in PCM than in nonpathologic breast tissue. However, no significant differences in ICAM-2 and E-selectin immunoreactivity were detected between ductal epithelium of PCM and non-PCM. ICAM-1, but not ICAM-2 or E-selectin, demonstrated significantly higher immunoreactivity in endothelial cells of PCM than in nonpathologic breast (P < .001). These results all suggest that ICAM-1 in both ductal epithelium and endothelium plays important roles in the inflammatory process of PCM, possibly through margination, extravasation, and attachment of plasma cells and lymphocytes, which may result in continuous inflammatory cell homing to ductal epithelial cells.