CD27 and COVID-19: In addition, critically ill COVID-19 is associated with a variety of lung pathologies, including inflammation-led diffuse alveolar damage and acute respiratory distress syndrome.[33] In critically ill COVID-19 patients, hypoxic microenvironments may induce cellular dormancy or promote the emergence of an aggressive, drug-resistant phenotype, thereby increasing the potential for subsequent tumor relapse.[34] Pathways involving CD27 and IgD- CD27- AC cells are of particular interest; however, current literature lacks studies directly examining their roles in HER2-positive breast cancer