The study is designed as international, prospective, minimal interventional study in cooperation with EUBREAST e.V. (European Breast Cancer Research Association of Surgical Trialists). Furthermore, it is planned to initiate a registry for postoperative breast seromas.

Postoperative seroma formations are one of the most common and serious complications after breast surgery, above all after mastectomy. Especially in patients who have opted for breast reconstruction using implants, seromas lead to infections and wound dehiscence which can result in implant and finally breast loss. To date, the cause of seroma development has not yet been clarified. First data of a pilot study of our research group identified an association with immunological-inflammatory processes as a possible cause for seroma development (Seroma after Simple Mastectomy in Breast Cancer-The Role of CD4+ T Helper Cells and the Evidence as a Possible Specific Immune Process; Pochert et al. 2022).

The main objective of the SerMa (Seroma of the Mammary gland) study presented here is to identify patient groups who have an increased risk of developing seromas based on immunological/inflammatory processes. Based on the findings clinical consequences should be developed in the future, such as more precise risk-adapted patient education and individualized advising regarding the selection of the reconstruction procedure, with the goal of minimizing complication rates. In addition, analyses of the tumor and the microenvironment will be performed to differentiate possible carcinoma-specific immunological processes.

Inclusion criteria study group and control group 1:

• Written informed consent
• Age ≥ 18 years
• all stages of DCIS or primary breast cancer (T1-T4, N0 or N+, M0) including all histopathological subtypes (ER/PR positive, ER positive/PR negative, Her-2/neu positive and triple negative)
• Surgical procedure planned including ablatio or subcutaneous mastectomy with implant or expander insertion

Inclusion criteria control group 2 and 3:

• Written informed consent
• Age ≥ 18 years
• Surgical procedure planned with implant or expander insertion with or without subcutaneous mastectomy

Exclusion criteria:

• Age <18 years
• Male sex
• Breast cancer patients planned for breast conserving therapy
• Recurrent breast cancer disease
• History of breast surgery
• Diagnosis of LCIS only
• Pregnancy at time of diagnosis
• Patients with a known immunodeficiency