Introduction: Early postoperative inflammation after lumpectomy may be influenced by tumor biology, particularly estrogen receptor expression, which modulates immune signaling and cytokine activity. However, its relationship with surgical inflammation remains unclear. This study aimed to evaluate the association between estrogen receptor expression and inflammatory responses during the first 24-hour postoperative period.

Material and methods: This descriptive cross-sectional study was conducted at Tabriz University of Medical Sciences in 2026 on 45 women undergoing lumpectomy, selected by convenience sampling. Estrogen receptor expression was assessed immunohistochemically in surgical specimens, while early postoperative inflammation was evaluated by 24-hour serum C-reactive protein measurement. Additional variables included age, body mass index, menopausal status, tumor characteristics, operative duration, white blood cell count, temperature, drainage volume, and pain score.

Results: Our study demonstrated that ER-negative patients exhibited a more pronounced inflammatory response post-lumpectomy. The ER-negative group showed significantly higher 24-hour CRP (16.83 vs. 12.46 mg/L; p=0.001) and WBC counts (10.08 vs. 8.71 × 10³/µL; p=0.017) than ER-positive patients. Regression analysis confirmed an independent inverse association between ER expression and postoperative CRP levels (adjusted β=3.92; p=0.003), underscoring a distinct link between molecular phenotype and acute systemic inflammatory intensity.

Conclusion: ER-negative status in breast cancer patients significantly exacerbates the systemic inflammatory response during the first 24 hours after lumpectomy. This association suggests that ER expression serves as a critical molecular biomarker for early postoperative recovery. Consequently, patients with ER-negative tumors may require heightened clinical surveillance and targeted anti-inflammatory interventions to manage the observed surge in acute inflammatory markers following surgical resection.