The collective of the SerMa pilot study included 100 cases of primary breast cancer or Carcinoma in situ who had undergone a mastectomy procedure with or without reconstruction of the breast using an implant or expander at Augsburg University Hospital between 12/2019 and 12/2022. The study aimed to investigate possible causes of seroma formation; reported here are the clinicopathological correlations between seroma formation and tumor biology and surgical procedures. Seroma occurred significantly more often in patients with older age (median patient age in cases with seroma was 73 years vs. 52 years without seroma; p < 0.001). In addition, patients with larger mastectomy specimen were significantly more likely to develop seroma (median ablation weight in cases with seroma 580 g vs. 330 g without seroma; p < 0.001). Other significant parameters for seroma formation were BMI (p = 0.005), grading (p = 0.015) and tumor size (p = 0.036). In addition, with insertion of implant or expander, a seroma occurred significantly less frequently (p < 0.001). In a binary logistic regression, age in particular was confirmed as a significant risk factor. In contrast, tumor biological characteristics, number of lymph nodes removed or affected showed no significant effect on seroma formation. The present study shows the need for patient education about the development of seroma in particular in older patients and patients with large breast volumes within the preoperative surgical clarification. These clinicopathological data support the previously published results hypothesizing that seroma formation is related to autoimmune/inflammatory processes and will be tested on a larger collective in the planned international multicenter SerMa study.

Abstract Background The primary objective of the SerMa pilot study was to identify possible immunological or inflammatory factors related to seroma formation after mastectomy in cases with primary breast cancer. Preliminary data suggest a distinct association between age and seroma formation. The work presented here investigates therefore a possible link between age and differences in the microenvironment represented by tumor-associated macrophages. The latter have been characterized by the expression of CD68 and CD163 receptors, that are markers of cells from the monocyte/macrophage lineage with known clinical implications. Methods Tumor tissue of 80 primary breast cancer cases of the SerMa pilot study was available for further analyses. Immunohistochemistry based on antibody staining against CD68 and CD163 was used and due to the mean age of 63 years two groups were formed and compared: patients aged under 63 and patients aged 63 and older. The number of macrophages (standardized manually quantified) was compared in these two groups regarding seroma formation. Results Seroma formation occurred significantly more frequently with older age of the patient (p < 0.001). For the overall cohort, the number of CD68-positive macrophages was significantly increased (p=0.036) in patients with seroma formation, as well as for CD163 (p=0.027). The macrophage polarization was shown to be independent of tumor biological characteristics (p > 0.130). However, closer examination revealed an age-dependent effect of the macrophage polarization. In the group 63 years and older, there was no significant difference in the number of CD68- or CD163-positive macrophages (p = 0.610 and p = 0.425, respectively) in relation to seroma formation. A significant effect was seen in this analysis only in patients younger than 63 regarding CD163 (p < 0.001) and a non-significant trend for CD68 (p = 0.065). Conclusions These data demonstrate an age-dependent significant correlation of CD163 positive macrophages measured in the tumor environment with seroma formation in the breast after mastectomy. For CD68 positive macrophages a trend was seen, but didn’t reach statistical significance due to the small number of cases. These data show a different immunological response in tumor tissue depending on age and therefore support the thesis that seroma formation is primarily related to immunological/inflammatory processes. In the future, detection of CD163-positive macrophages in the tumor microenvironment could therefore be considered a marker for patients under 63 years at increased risk of seroma. The planned international SerMa study (EUBREAST 5) will have to show whether these results can be transferred to a prospective design with higher case number. Citation Format: Melitta Koepke, Felicitas Schneider, Christina Kuhn, Mathis Wild, Mariella Schneider, Nicole Pochert, Claudia Traidl-Hoffmann, Jacqueline Sagasser, Christian Dannecker, Christian Hinske, Maggie Banys-Paluchowski, Michael Untch, Thorsten Kühn, Udo Jeschke, Nina Ditsch. SerMa (Seroma of the Mammary gland) pilot - Is there a possible link between macrophage-based immune response and age? [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-25-06.

Purpose The development of a seroma after breast cancer surgery is a common postoperative complication seen after simple mastectomy and axillary surgery. We could recently demonstrate that breast cancer patients undergoing a simple mastectomy with subsequent seroma formation developed a T-helper cell increase within the aspirated fluid measured by flow cytometry. The same study revealed a Th2 and/or a Th17 immune response in peripheral blood and seroma fluid of the same patient. Based on these results and within the same study population, we now analyzed the Th2/Th17 cell associated cytokine content as well as the best known clinical important cytokine IL-6. Methods Multiplex cytokine measurements (IL-4, IL-5, IL-13, IL-10, IL-17, and IL-22) were done on 34 seroma fluids (Sf) after fine needle aspiration of patients who developed a seroma after a simple mastectomy. Serum of the same patient (Sp) and that of healthy volunteers (Sc) were used as controls. Results We found the Sf to be highly cytokine rich. Almost all analyzed cytokines were significantly higher in abundance in the Sf compared to Sp and Sc, especially IL-6, which promotes Th17 differentiation as well as suppresses Th1 differentiation in favor of Th2 development. Conclusion Our Sf cytokine measurements reflect a local immune event. In contrast, former study results on T-helper cell populations in both Sf and Sp tend to demonstrate a systemic immune process.