CNN2 and breast carcinoma: Identifying serum biomarkers like calponin-2 could aid in diagnosis, tumor burden assessment, and prognosis.<h4>Objective</h4>To estimate serum calponin-2 levels in patients with breast carcinoma and evaluate correlations with clinicopathological parameters.<h4>Patients and methods</h4>This prospective observational study was conducted at Jawaharlal Nehru Medical College, Aligarh Muslim University, from May 2023 to May 2025.