
==== Front
Cancer Immunol Immunother
Cancer Immunol Immunother
Cancer Immunology, Immunotherapy : CII
0340-7004
1432-0851
Springer Berlin Heidelberg Berlin/Heidelberg

39235656
3783
10.1007/s00262-024-03783-6
Research
Distribution characteristics of immune infiltration and lymphovascular invasion in patients with breast cancer skin recurrence
Zhou Danyang 12
Li Mei 1
Wu Wei 1
Wu Ying 3
Nong Qiaohong nongqh2021@163.com

2
Wang Shusen wangshs@sysucc.org.cn

1
Hong Ruoxi hongrx@sysucc.org.cn

1
1 grid.488530.2 0000 0004 1803 6191 Department of Medical Oncology, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-Sen University Cancer Center, Guangzhou, 510000 China
2 https://ror.org/03kkjyb15 grid.440601.7 0000 0004 1798 0578 Department of Oncology, Peking University Shenzhen Hospital, Shenzhen, China
3 grid.452847.8 0000 0004 6068 028X Department of Interventional Therapy, Shenzhen Second People’s Hospital, The First Affiliated Hospital of Shenzhen University, Shenzhen, China
5 9 2024
5 9 2024
11 2024
73 11 2234 6 2024
17 7 2024
© The Author(s) 2024
2024
https://creativecommons.org/licenses/by-nc-nd/4.0/ Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/.
Background

To assess the distribution characteristics of immune infiltration and lymphovascular invasion in breast cancer skin recurrence patients.

Methods

We retrospectively analyzed the clinicopathological data of patients who underwent radical surgery for primary breast cancer and experienced skin recurrence between January 2001 and April 2019. Immune and lymphovascular biomarkers were quantified in primary breast cancers, skin lesions and visceral metastatic lesions. Differences in biomarkers distribution between matched tissues were statistically analyzed using the Wilcoxon signed-rank test and Kruskal–Wallis one-way ANOVA.

Results

A total of 71 female breast cancer patients were reviewed in this study. Our study found that the expression levels of various lymphocyte immune markers in primary tumor specimens were higher than those in skin recurrences. The expression of CD8, CD57 and CD31 in primary breast cancer was higher than those in the skin. Compared to visceral metastatic lesions, D2-40 was highly expressed in the skin, while CD8 tended to decrease. In the skin specimens, the expression of CD8 (P < 0.001), FOXP3 (P = 0.006) and CD68 (P < 0.001) in the intratumoral area was higher, while the expression of CD57 (P < 0.001) was higher in the peritumoral area. Analyzing specimens from the same patient at different time points of skin progression, it was found that the expression of peritumoral CD4 decreased (P = 0.044) as the disease progressed. The low expression of D2-40 and CD163 in the skin lesions suggested a decrease in DFS.

Conclusion

The immune microenvironment of breast cancer skin recurrence may be in a state of suppression, and this suppression may intensify with disease progression. The pattern of skin recurrence may be more inclined toward lymphatic invasion. Our study provides new insights into the biological behaviors of this disease and its response to immunotherapy.

Keywords

Skin recurrence
Immune infiltration
Lymphovascular invasion
Breast cancer
Prognosis
Natural Science Foundation of Guangdong Province2019A1515011945 2020A1515010105 Wang Shusen Hong Ruoxi issue-copyright-statement© Springer-Verlag GmbH Germany, part of Springer Nature 2024
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pmcIntroduction

In 2020, breast cancer was the most prevalent and deadliest cancer among women globally [1]. Approximately 5%–40% of breast cancer patients experience recurrence in the chest wall [2–5]. Based on the depth of lesion involvement, it can be classified into involvement of subcutaneous tissue, skin or both. The skin, with its complex network of diverse cell types and the flexibility of blood vessels and lymph nodes, plays a significant role in maintaining vital bodily functions and the progression of tumors [6–10]. Our previous research indicated that skin involvement is a predictor of poor disease control in patients with chest wall recurrence and is closely related to continuous chest wall progression [11]. In skin recurrence of breast cancer, about one-third of patients have metastatic lesions confined only to the skin. Compared to most tumors, skin recurrence in breast cancer has a relatively weaker association with visceral metastasis. Compared to other metastatic lesions of breast cancer, low levels of tumor-infiltrating lymphocytes (TILs) and high expression of FOXP3 in the skin seem to provide an immunosuppressive microenvironment for the growth of tumor cells [12]. The interaction between tumor cells and certain chemokines and their receptors secreted by the dermis or epidermis is involved in the homing mechanism of metastatic cells to the skin [13]. At the same time, the structural and functional units formed by the regional distribution of dermal lymphatic vessels may also provide a favorable environment for the colonization and survival of tumor cells in the skin [14].

Breast cancer is generally considered to be a tumor with low immunogenicity. However, evidence suggests that the quantity and phenotype of TILs can predict the clinical prognosis and therapeutic efficacy of breast cancer patients [15, 16]. Helper T cells (Th) are key regulatory factors in the host’s anti-tumor immunity, mainly comprising two specific subsets: Th1 and Th2 cells. The expression of Th1 cells and Th2 cells, as well as the balance between Th1 and Th2, play a crucial role in anti-tumor immunity and are commonly used as indicators of the immune status of tumor patients [17, 18]. CD8 + T cells are key immune cells in killing tumor cells that present major histocompatibility complex (MHC) class I molecules, and CD8 + cytotoxic T lymphocytes (CTLs) are essential for tumor destruction [19]. In a large study including 1334 patients with invasive breast cancer, an increase in expressed CD8 + T cells indicated improved clinical prognosis, and an increase in the proportion of intratumor CD8 + T cells was associated with an increased breast cancer-specific survival rate (HR = 0.55, 95% CI 0.39–0.78, P = 0.001) [20]. Another study assessing the immune microenvironment in more than 200 breast cancer patients showed that patients with more than 15 FOXP3 + cells had shortened recurrence-free survival (HR = 1.58, 95% CI 1.01–2.47, P = 0.040) and a trend toward reduced overall survival (OS) (HR = 1.62, 95% CI 0.96–2.74, P = 0.070), suggesting that the presence of Th2 marker FOXP3 + in tumors is associated with a poorer prognosis [21]. The tumor immune microenvironment (TIME) plays critical roles in tumor survival, progression and targeted imaging of TIME biological molecules by various modalities which can be used for the early detection of cancer [22]. Furthermore, immunotherapy, which leverages the body’s defense mechanisms to recognize and combat cancer cells, has become an integral part of cancer research by modulating the immune system to directly target and fight tumor cells [23].

Skin recurrence in breast cancer typically occurs in anatomical areas close to the primary tumor, with the chest wall being the most common site. Breast cancer tumor cells can colonize and invade skin tissue through lymphatic and hematogenous routes. Skin recurrence may occur during the widespread dissemination of the tumor or may be the only sign of disease metastasis. What differences are there between the tumor microenvironment changes caused by breast cancer cells colonizing and invading skin tissue and those at the primary tumor site and visceral metastatic lesions? Therefore, the current study monitors the differences in the tumor immune microenvironment and lymphovascular invasion of matched breast cancer tissues, skin recurrence and visceral metastatic tissues, and tracks the temporal and spatial evolution characteristics of TILs during the progression of chest wall disease, to identify biomarkers that may indicate different clinical outcomes and provide new insights for future immunotherapy.

Patients and methods

Patients

We reviewed the clinical and pathological data of Asian female breast cancer patients with chest wall recurrence who visited the Sun Yat-sen University Cancer Center from January 2001 to April 2019. Patients meeting all the following criteria were included in this study: (1) patients with pathologically confirmed breast cancer, (2) those who underwent modified radical surgery or breast-conserving surgery for their primary breast tumor, (3) no evidence of distant organ (including distant lymph nodes) metastasis at initial diagnosis, (4) histologically confirmed chest wall recurrence involving the skin and (5) sufficient pathological samples available for subsequent immunohistochemical analysis. Patients were excluded from this study if they were male, had severe systemic diseases, a second primary malignant tumor or concurrent distant metastasis (distant metastasis was defined as metastasis to visceral organs, bones, soft tissues and non-regional lymph nodes). This study recorded and analyzed all the clinical pathological data of included patients. We retrieved tissue specimens from the pathology department, including paired primary tumor, skin recurrence and visceral metastasis specimens. Disease-free survival (DFS) was the time from radical resection for the first skin recurrence to the second progression of chest wall, and progression-free survival (PFS) was defined as the time from the diagnosis of locally unresectable skin recurrence to the second chest wall progression. OS referred to the time from chest wall recurrence to death from all causes. All patients were followed up regularly until death or the study data cutoff (March 1, 2024). The study was approved by the Ethics Committee of the Sun Yat-sen University Cancer Center (protocol code B2020-051-01, approval date February 10, 2021). As part of routine clinical practice, all subjects involved in this retrospective study provided informed consent.

Clinicopathological data

For the quantitative assessment of immune and lymphovascular markers, we retrieved formalin-fixed paraffin-embedded (FFPE) tissues from the pathology department for immunohistochemical testing, which included the following markers: immune markers (PD-1, PD-L1, CD4, CD8, FOXP3, CD68, CD163 and CD57) and lymphovascular markers (CD31 and D2-40). Immune cells in the skin recurrence and matched primary and visceral metastatic lesion specimens were evaluated for CD4, CD8, FOXP3, CD68, CD163 and CD57 markers, distinguishing between peritumoral and intratumoral areas. The evaluation method for the aforementioned markers involved randomly selecting three areas (1 mm2), counting the number of positive cells under a 200 × magnification and taking the average of the three fields as the final positive cell density score. The expression of PD-1 and PD-L1 in tumor cells and immune cells was reported as the percentage of positive cells on each slide. To analyze tumor-associated angiogenesis and lymphangiogenesis, microvessel density (MVD) and lymphatic microvessel density (LVD) in the tumor tissue were calculated by quantifying CD31-positive vessels and D2-40-positive vessels, respectively. For the assessment of CD31 and D2-40, the three areas with the highest vascular density within the tumor (hotspots) were identified under 25 × magnification, and the average count was taken after manual counting under 200 × magnification (0.25 mm2). Except for the routine molecular typing markers of breast cancer reported in pathology reports, all other markers’ immunohistochemical assessments were independently completed by two experienced pathologists, with the average score of the two taken as the final score for each sample. If the discrepancy exceeded 20%, the two observers discussed the results in order to reach a consensus.

Statistical analysis

Continuous variables were represented by medians and ranges, while categorical variables were expressed as percentages. The cutoff values for biomarkers were determined using the median value. Differences in immune infiltration distribution between matched tissues were statistically analyzed using the Wilcoxon signed-rank test and Kruskal–Wallis one-way ANOVA. The impacts of clinical pathological factors on DFS, PFS and OS were calculated using the Kaplan–Meier curve analysis. For all statistics, a P-value of less than 0.05 was considered statistically significant, and all P-values were two-sided. Statistical analysis was performed using SPSS statistical software version 25.0 and GraphPad Prism software version 6.0.2.

Results

Patient characteristics

Between January 2001 and April 2019, a total of 71 Asian female breast cancer patients who met the inclusion criteria were enrolled in this retrospective study at the Sun Yat-sen University Cancer Center. The median age at initial diagnosis for these 71 patients with breast cancer chest wall recurrence was 48 (range, 27–71 years). Invasive ductal carcinoma (n = 68, 95.8%) was the main pathological subtype of the primary breast tumor in these patients. The histological grades of the included patients were II (n = 33, 46.5%) and III (n = 38, 53.5%). Lymph node positivity was present in 80.3% of the patients. Among these 71 patients, 68 had undergone modified radical surgery for their primary breast tumor, while the remaining three patients underwent breast-conserving surgery. Thirty of the patients had primary tumors involving the skin, classified as pT4; the other 41 patients did not have primary breast cancer tumors involving the skin. The median time to chest wall recurrence from the initial diagnosis of breast cancer was 16.1 months, and the median follow-up time was 51.0 months.

We further explored the differences in pathological factors between the primary breast lesion and the paired chest wall skin lesions (Table 1). We found that the expression of estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2) in the primary tumor and chest wall skin tissues did not differ, while the proportion of high Ki-67 expression was significantly increased in the chest wall skin tissues, with statistical significance (P = 0.031). There were no significant differences in the expression of neural invasion, inflammatory cells and the number of tumor emboli in the paired primary tumor and skin recurrence. Mitotic figures were less frequent in the chest wall skin specimens (P = 0.022). Calcification (P < 0.001) and necrosis (P < 0.001) were more commonly observed in the primary breast tissues.Table 1 Comparison of pathological characteristics between paired primary breast and skin recurrence

Factor	Primary site	Chest wall	P	
ER			0.417	
 < 1%	33	24		
 >  = 1%	36	35		
PR			0.345	
 < 1%	34	34		
 >  = 1%	35	25		
HER2			0.251	
Positive	30	19		
Negative	37	36		
Ki-67			0.031	
 < 15%	10	2		
 >  = 15%	50	49		
Mitotic figure/10HPF			0.022	
 < 15	18	31		
 >  = 15	53	40		
Neurological invasion			0.330	
Yes	15	20		
No	56	51		
Calcification			 < 0.001	
Yes	14	0		
No	57	71		
Necrosis			 < 0.001	
Yes	45	19		
No	26	52		
Inflammatory cell ratio			0.735	
 < 10	30	32		
 >  = 10	41	39		
Tumor embolus count			0.128	
 <  = 5	27	36		
 > 5	44	35		
Bold values indicate the statistically significant value of p < 0.05

Immune and lymphovascular markers in skin recurrence tissues

Immunohistochemical analysis of these tissue samples was performed to assess immune infiltration and lymphovascular markers. Table 2 summarizes the median and interquartile range of expression levels for various biomarkers in the intratumoral and peritumoral areas of the primary lesions and skin tissues from the 71 patients. The expression of various lymphocyte immune markers in primary tumor specimens was higher than in skin lesions. Tumor-associated lymphocytes and tumor-associated angiogenesis showed different distributions in matched tissues and regions. Comparing the paired primary tumors and chest wall tissues (Fig. 1), the expression of CD8 and CD57 in both the intratumoral and peritumoral areas of the primary tumors was higher than that in the skin tissues (CD8: intratumoral P = 0.001, peritumoral P = 0.003 and CD57: intratumoral P = 0.002, peritumoral P = 0.003). Additionally, the expression of FOXP3 in the intratumoral area (P = 0.021) and CD68 (P = 0.036), CD163 (P = 0.025) in the peritumoral area was also higher in the primary lesion than in the skin tissue. The tumor-associated angiogenesis marker CD31 (P = 0.011) was also more abundant in the primary lesion. We found that in the skin recurrence specimens, the expression of CD8 (P < 0.001), FOXP3 (P = 0.006) and CD68 (P < 0.001) in the intratumoral area was higher than in the peritumoral area, while the expression of CD57 (P < 0.001) was higher in the peritumoral area than in the intratumoral area (Fig. 2). Among the 22 patients who had two skin recurrence specimens, we also analyzed specimens from different times of skin progression in the same patient (Fig. 3) and found that the distribution of peritumoral CD4 varied among different chest wall tissues: As the chest wall progressed, the expression of peritumoral CD4 decreased (P = 0.044). We compared the immune and lymphovascular markers in the chest wall skin tissue and visceral metastatic lesions of five patients who had matched visceral metastatic tissues. We found that D2-40 was highly expressed in the skin tissue of all five patients, while CD8 was highly expressed in the visceral metastatic lesions of four patients (Fig. 4).Table 2 Summary of biomarker expression in intratumoral and peritumoral areas of the primary lesion and skin recurrence tissues

Factor	Primary lesion	Chest wall tissues	P	
CD4	
Intratumoral regions	7.00 (2.00–20.00)	6.00 (2.00–20.50)	0.556	
Peritumoral regions	12.00 (5.00–24.50)	10.00 (4.00–19.00)	0.133	
CD8	
Intratumoral regions	135.00 (70.25–227.50)	62.50 (30.00–111.25)	0.001	
Peritumoral regions	40.00 (23.00–80.00)	29.00 (19.00–40.00)	0.003	
FOXP3	
Intratumoral regions	4.00 (1.00–7.00)	1.00 (0.00–3.25)	0.021	
Peritumoral regions	1.00 (0.00–4.00)	0.00 (0.00–2.00)	0.377	
CD68	
Intratumoral regions	5.50 (0.00–38.00)	8.50 (1.00–33.25)	0.361	
Peritumoral regions	6.00 (0.00–21.25)	2.50 (0.00–8.00)	0.036	
CD163	
Intratumoral regions	136.00 (100.00–200.00)	140.00 (82.00–200.00)	0.752	
Peritumoral regions	180.00 (12.00–220.00)	120.00 (85.00–200.00)	0.025	
CD57	
Intratumoral regions	2.00 (0.00–4.00)	1.00 (0.00–2.00)	0.002	
Peritumoral regions	3.00 (1.00–5.00)	2.00 (1.00–3.50)	0.003	
PD-1	
Tumor cell	0.00 (0.00–0.00)	0.00 (0.00–0.00)	0.152	
Immune cell	35.00 (15.00–60.00)	30.00 (9.50–40.00)	0.066	
PD-L1	
Tumor cell	0.00 (0.00–0.00)	0.00 (0.00–0.00)	0.663	
Immune cell	0.00 (0.00–5.75)	0.00 (0.00–10.00)	0.123	
CD31	68.00 (44.00–90.00)	51.00 (32.00–90.00)	0.011	
D2-40	10.00 (7.00–13.00)	10.00 (7.00–12.00)	0.576	
Bold values indicate the statistically significant value of p < 0.05

Fig.1 Differential expression of immune and vascular markers in matched primary tumors and skin recurrence

Fig.2 Differential expression of immune markers in intratumoral and peritumoral regions of skin recurrence tissue

Fig.3 Differential expression of CD4 in the peritumoral area in skin recurrence tissue from the same patient at different time periods

Fig.4 Differential expression of CD8 and D2-40 in the skin recurrence and visceral metastasis from the same patient

Prognostic value of immune and lymphovascular markers

In the 71 included patients, 40 underwent local radical surgery after skin recurrence, while the remaining 31, due to extensive recurrence range and/or a large number of recurrent lesions, only underwent skin lesion biopsy after recurrence and did not receive local radical surgery. Among the 40 patients who underwent radical surgery, the 1-year DFS rate was 53%, which decreased to 49% at 2 years and 44% at 3 years; the OS rate at 5 years was 91%. For the remaining 31 patients, PFS rate at 3 months was 63%, dropping to 43% at 6 months and 29% at 12 months; the corresponding 1-year, 3-year and 5-year OS rates were 90%, 68% and 43%, respectively. Patients with low D2-40 expression in the chest wall skin tended to have a poorer DFS compared to those with higher percentages (P = 0.044). Similarly, a lower number of CD163-positive cells in the skin lesions also indicated a poorer DFS (P = 0.050) (Fig. 5). For PFS and OS, other immunological and vascular indicators in the chest wall skin tissue did not effectively predict clinical prognosis.Fig.5 Kaplan–Meier curve for DFS stratified by D2-40 and CD163 of skin recurrence lesions

Discussion

Breast cancer patients with skin recurrence form a heterogeneous group, posing a severe challenge to treatment strategies. Here, we aim to summarize the clinical and pathological characteristics of patients with skin recurrence in breast cancer, as well as the changes in the immune microenvironment and lymphovascular invasion of the primary tumor and visceral metastatic lesions, to provide new insights for patient clinical prognostic stratification and personalized treatment. In this study, we found that the tumor microenvironment of skin recurrence might be in an immunosuppressive state. Compared to the primary tumor and visceral metastatic tissues, the expression of CD8 in chest wall skin lesions was decreased. There were temporal and spatial differences in the distribution of TILs within skin recurrence lesions. As the disease progressed, the expression of peritumoral CD4 in the chest wall skin lesions of the same patient decreased. The pattern of skin recurrence in breast cancer might be more inclined toward lymphatic invasion than vascular invasion. Compared to the primary lesion and visceral metastatic lesions, CD31 expression was decreased, and D2-40 expression was increased in skin recurrence.

The previous literature rarely discussed the intrinsic mechanisms of malignant tumors involving the skin. The complex network of various cell types and the flexibility of skin blood vessels and lymph nodes maintain several important processes such as inflammation, immune responses, wound healing and angiogenesis [6–10]. CD8 + cytotoxic T cells, through specific interactions between antigens and T-cell receptors (TCR), recognize foreign antigens associated with MHC class I molecules [24]. Cytotoxic T cells, as the main effector component of the adaptive immune system, act on tumor cells that can present aberrant antigens [25, 26]. The significantly lower expression of CD8 in skin lesions compared to primary tumors in our study suggested a reduced anti-tumor immune response in skin tissues. The CD57 antigen, also known as HNK-1, LEU-7 or L2, is commonly reported as a marker for human natural killer cells [27]. NK cells have potent cytolytic activity against tumors and can control tumor growth and metastatic spread [28]. The expression of CD8 and CD57 in both intratumoral and peritumoral areas of skin tissues was lower than that in primary breast tissues, suggesting that the immune microenvironment of skin recurrence might be in a relatively suppressed state. Compared to the visceral metastatic tissues, the expression of CD8 in skin lesions was decreased. The literature comparing skin metastases of breast cancer with other metastatic lesions found that skin metastases had the lowest levels of TILs, with a higher FOXP3 and lower CD8/FOXP3 ratio [12]. This suggested that skin tissue provided a more lenient immune microenvironment for tumor growth. The physiological relief of cytotoxic immune activity in skin tissue through different immunosuppressive mechanisms was referred to as “immune privilege” [29, 30]. In our current study, comparing matched primary tumors and skin tissues, the expression of various lymphocyte immune markers in primary tumor specimens was higher than those in skin recurrence. Regulatory T cells expressing FOXP3 induce host tolerance to tumor antigens by dampening T cell-mediated immune responses against tumor cells, thus promoting tumor growth [31]. Macrophages can have both tumoricidal effects and participate in tumor-promoting activities. CD68 and CD163 are considered to be highly specific monocyte/macrophage markers that can identify M1 and M2 macrophages [32]. Type 1 macrophages are usually activated during antigen presentation and inflammatory responses [33], while Type 2 macrophages may be involved in tumor growth, angiogenesis, invasion and metastasis and therapy resistance [34, 35]. The differentiation of tumor-associated macrophages (i.e., M1 or M2 phenotype) is associated with different clinical prognoses [36, 37]. In terms of the regional distribution of immune infiltration, in skin tissues, the expression of CD8, FOXP3 and CD68 in the intratumoral area was significantly higher than in the peritumoral area, while the expression of CD57 in the intratumoral area was lower than in the peritumoral area. This meant that there was a significant difference in the distribution of immune cells between the intratumoral and peritumoral areas of chest wall tumors, possibly due to the different intensities of immune responses in the two areas [38]. Although various immune cells have different functions and have contradictory effects in immune responses, one of the reasons for the low expression of immune markers in skin recurrence might be due to the overall lower immune level of the lesion. The role of CD4 + TILs in breast cancer is complex. CD4 + T cells exert direct anti-tumor effects by blocking the progression of the cancer cell cycle at the G1/S phase, and they induce T cell-dependent tumor regression through indirect pro-inflammatory/immune effects [39]. In our study, as the skin disease progressed, the expression of CD4 in the peritumoral area decreased. Above, there were temporal and spatial differences in the distribution of TILs in skin recurrence lesions.

Structurally, the skin can be divided into the epidermis and dermis. Skin recurrence in female breast cancer mainly occurs through hematogenous and lymphatic routes [40, 41]. The number of tumor microvessels and microvessel density (MVD) is obtained from CD31 immunohistochemistry. The expression of CD31 in skin recurrence samples was lower than in primary breast cancer tissues. D2-40 can specifically label lymphatic endothelial cells, which is an important marker for the detection of lymphatic vessel invasion [42]. Compared to visceral metastatic tissues, lymphatic-associated marker D2-40 was highly expressed in skin lesions, suggesting that the skin recurrence pattern of breast cancer may be more inclined to lymphatic invasion than vascular invasion. Furthermore, a certain proportion of breast cancer patients with chest wall recurrence will experience disease progression within a short time after local or systemic treatment. Our previous study found that patients with skin involvement were more likely to have purely persistent breast cancer chest wall progression [11], which might be related to lymphatic vessel invasion [42].

We found within patients with skin recurrence, low expression of D2-40 and CD163 showed poorer DFS. Despite the D2-40 IHC marker being helpful in the diagnosis and confirmation of lymphatic vessel invasion in invasive breast cancer, few articles have reported a direct association between D2-40 and the prognosis of breast cancer. Traditionally, CD163-positive tumor-associated macrophages (TAMs) within the tumor microenvironment are associated with unfavorable prognosis. The suppressive immune microenvironment in the skin, along with its rich vascular and lymphatic systems, as well as the specific subsets and localization of TAMs in the tumor microenvironment [43], all influence the clinical prognosis of patients. Indeed, further research is needed to verify this.

The treatment of skin recurrence in breast cancer is complex. Chest wall resection is disfiguring and associated with significant complications [44]. The overall response rate for second-line and third-line salvage chemotherapy is at most 20%–30% [45]. With the increasing understanding of the complex pathobiology of skin recurrence in breast cancer, it is essential to fully comprehend the dynamic interactions between cancer and immune cells, making immunotherapy a promising therapeutic approach.

The current study has several limitations. Like any retrospective clinical study analysis, the included population spans nearly 20 years, with incomplete clinicopathological information, the loss of paired tumor specimens and degradation of tumor tissue reducing the number of included samples. As the research was based on historical data, there might be biases in data collection and recording, as well as uncontrollable confounding factors. With the updating of guidelines, not all included patients received the same treatment and treatment plans after chest wall recurrence. In addition, a multicenter study would make the results of this study more convincing. We acknowledge the limitations of this study, but its results help with individualized treatment decisions for patients with skin recurrence in breast cancer and provide a reference for future research on breast cancer patients with skin recurrence.

Conclusion

Skin recurrence in breast cancer has gradually received more attention due to its clinical heterogeneity and the complexity of treatment. We found that the immune microenvironment of skin lesions might be in a state of suppression, and as the disease progressed, the state of immune suppression in the skin lesions might intensify. Skin recurrence pattern of breast cancer might be more inclined to lymphatic invasion than vascular invasion. Our study provided new insights into understanding the biological behavior of this disease and also offered significance for early screening related to the immune microenvironment and for immunotherapy.

Author contributions

DYZ and WW for acquisition of data, analysis and interpretation of data. DYZ generated the charts according to clinical information and drafted the manuscript. ML and YW for immunohistochemical evaluation of the markers. RXH, SSW and QHN for study conception and design, obtained funding and study supervision. All the authors reviewed the manuscript.

Funding

This work was supported by the [Natural Science Foundation of Guangdong Province] under Grant [number 2019A1515011945 and 2020A1515010105].

Data availability

The datasets used and/or analyzed during the current study are available from the corresponding author upon reasonable request.

Declarations

Conflict of interest

The authors declare no competing interests.

Ethics approval

The study was approved by the Ethics Committee of Sun Yat-sen University Cancer Center (No. B2020-051–01, approval date February 10, 2021).

Informed consent

The informed consent was obtained for inclusion with human subjects.

Publisher's Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Danyang Zhou, Mei Li and Wei Wu have contributed equally to this work as first authors.
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