Degnim, Amy C.

Abstract Introduction: Benign breast disease (BBD) is an important breast cancer (BC) risk factor, which may be classified as non-proliferative disease (NPD), proliferative disease without atypia (PDWA), or atypical hyperplasia (AH) for risk stratification. Data related to the frequency of specific types of BBD and their relationship to BC risk in the Hispanic American population are limited. To address this knowledge gap, we compared BBD and associated BC risk among Hispanic white (HW) and non-Hispanic white (NHW) in New Mexico (NM). Methodology: A retrospective IRB-approved study was performed of women 19 years or older residing in six counties in NM (Bernalillo, Sandoval, Sante Fe, Socorro, Torrance, Cibola/Valencia) between 1996 and mid-2007 to compare the frequency of BBD subtypes and BC risk among HW and NHW. We excluded women who had a history of BC prior to BBD diagnosis or who were diagnosed with BC within 6 months after BBD biopsy. Race and ethnicity were self-reported by women at the time of biopsy. BBD was categorized as NPD, PDWA, or AH based on medical records. Incident BC (in-situ or invasive) was ascertained via linkage to the NM Surveillance Epidemiology End Results (SEER) Registry and BC risk was assessed using standardized incidence ratios (SIRs), comparing the observed number of BC events to that expected based on the NM SEER six-county race- and ethnicity-specific incidence rates, accounting for age and calendar period. Results: Our analysis included 3,870 HW and 6,996 NHW women with BBD. The HW were younger (47.1 vs. 51 years) compared to NHW. HW women had slightly more NPD (69.4% vs. 66.6%) but less PDWA (26.2% vs. 29.4%) and similar frequency of AH (4.3% vs. 3.9%) as compared to NHW. Over a median post-BBD follow-up period of 13 years (range 6 months-17 years), 644 BCs were observed (4.81% in HW and 6.55% in NHW). The observed BC risk among women with BBD was higher than population-based expected rates (SIR 1.98, 95% CI 1.82-2.13, p<0.001) and showed expected increases in risk with increasing degrees of BBD abnormality: SIR=1.90 for NPD, 2.00 for PDWA, and 3.01 for AH. Comparing BC risk by ethnic subgroups, HW women had an overall risk of BC after BBD that was statistically indistinguishable from NHW women (SIR=2.17, 95% CI 1.86-2.48 in HW women, and SIR=1.91, 95% CI 1.73-2.08 in NHW women). Within the major subgroups of the BBD findings, there were no significant differences in risk of BC after BBD for HW versus NHW women. Conclusions: In this population-based study, benign breast disease subtypes and their associated breast cancer risk were similar among the Hispanic and non-Hispanic white women. Citation Format: Kush Raj Lohani, Andrea M. Nibbe, Robert A. Vierkant, Laura M. Pacheco-Spann, Lisa R. Seymour, Celine M. Vachon, Mark E. Sherman, Amy C. Degnim, Deirdre Hill. Comparison of benign breast disease subtypes and breast cancer risk among Hispanic and non-Hispanic white women in New Mexico. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4213.

Abstract Purpose: Benign breast disease (BBD) is viewed as a non-obligate precursor stage in the development of breast cancer (BC). Transcriptome profiling using RNA sequencing (RNA-seq) of bulk formalin-fixed paraffin-embedded (FFPE) tissue blocks has been routinely used in BC research. However, RNA-seq of heterogeneous bulk samples represents an averaged expression profile across all cell mixtures. Downstream analyses, such as biomarker discovery, are likely confounded by differences in cell proportions. There is a lack of research in optimizing strategies for cell type deconvolution especially for FFPE samples. We evaluated and optimized strategies for cell type deconvolution using existing single cell RNA-seq (scRNA-seq) and single nucleus RNA-seq (snRNA-seq) breast tissue references, and applied these to a cohort of BBD FFPE samples to assess risk of subsequent BC. Methods: 7 scRNA-seq and 3 snRNA-seq public samples from women’s breast tissue were normalized using SCTransform, then integrated using Harmony to form a complete reference set. Bioinformatics evaluations examined the performance of existing statistical and deep learning-based deconvolution methods. Computational simulations were conducted to evaluate those methods on three scenarios: 1) baseline; 2) incomplete reference set; 3) FFPE artifacts. FFPE artifacts were simulated based on a generalized additive model using 7 in-house paired FFPE-fresh frozen samples. Finally, we applied the best performing method to our BBD cohort of 62 samples. Differential expression analysis adjusting for cell proportions was performed to identify transcriptomic aberrations in BBD cases. Results: snRNA-seq was more sensitive in capturing adipocytes, while scRNA-seq was more sensitive in detecting lymphocytes in breast tissue. The median number of detectable genes per cell was higher for scRNA-seq than snRNA-seq before integration (1264 vs 558). Marker gene-based regression methods (e.g. CIBERSORT) displayed higher variance and lower bias compared to methods directly using scRNA-seq data (e.g. SCDC). Incomplete reference data led to increased bias and little effect on variance. FFPE artifacts had a higher impact on performance compared to incomplete reference data. Overall, Scaden, a deep learning-based method, was the top performing method across all simulation scenarios and was especially robust to FFPE artifacts. 59 differential expressed genes (DEGs) were identified with fold change > 1.5 and p value < 0.01. DEGs involved in BC, e.g. S100A8, WNT4 and HIST1H3H, would be left out if cell proportions were not properly adjusted. Conclusions: We constructed the first complete single cell reference data for women’s breast tissue and benchmarked existing cell type deconvolution methods. Compared to analyses not adjusting for cell proportions, we observed substantial differences in perturbed genes and pathways associated with BC risk for BBD patients. Citation Format: Yuanhang Liu, Chen Wang, Stacey J. Winham, Aditya Bhagwate, Robert A. Vierkant, Julie M. Cunningham, Bryan M. McCauley, William A. Jons, Derek C. Radisky, Amy C. Degnim. Deconvolution of cell type composition in FFPE tissue: Application to benign breast disease. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4291.

Abstract Purpose: Young women’s breast cancers (YBCs), defined herein as breast cancer (BC) diagnosed at age ≤ 40 years, are etiologically and biologically distinct from postmenopausal BCs, demonstrating a higher proportion of estrogen receptor (ER) negative subtypes and a worse prognosis. Studies have not assessed whether risk factors such as recent parity and body mass index (BMI) are linked to protein expression profiles in YBCs. Accordingly, we examined protein expression assessed with GeoMx® Digital Spatial Profiling (DSP) in 640 YBCs prepared as tissue microarrays (TMAs) in the Young Women’s BC Study (YWBCS). Methods: The YWBCS is a multi-institutional cohort of 1,297 women with incident BC diagnosed at age <40 years identified through medical record review, with risk factor data collected via questionnaires. TMAs including 1,505 cores of 640 YBCs that were collected prior to therapy and were suitable for molecular analysis were evaluated for 72 markers with NanoString GeoMx DSP. Associations of log-transformed biomarker expression with BMI and time from last live birth to BC diagnosis were carried out using linear mixed modeling approaches, accounting for multiple tumor tissue cores per individual. Results: Mean age at BC was 35.5 years (range 17-40). Tumor subtypes based on clinical immunostaining were the following: luminal B 46%; luminal A 36%; triple negative 12% and HER2+ 6%. Of 72 biomarkers tested, 53 (74%) were evaluable after QC and normalization. GeoMx ER and PR protein levels were higher in luminal A and luminal B YBCs than in HER2+ and TNBC (p=2x10-94 and 2x10-52, respectively), supporting the accuracy of the GeoMx assay. Compared to nulliparas or those with most recent birth > 3 years before BC, those who gave birth ≤ 3 years prior to BC had tumors with higher expression of PR (8x10-6) and ER (p=0.006), and lower expression of BCL-2 (p=0.006). In contrast, women with last birth ≥ 6 years prior to BC had higher expression of CD8 (p=0.006) and PD-1 (p=0.001) than nulliparas and those with more recent births. Compared to women with BMI between 18.5 and 29.9, those with higher or lower BMIs had higher expression of CD34 (p=0.0003), CD4 (p=0.0009) and CD14 (p=0.001). BCL-2 expression was higher among women with BMI < 18.5 compared to those with higher values (p=0.005). Women with BMI of 30+ had higher β2-microglobulin levels than those with lower BMIs (p=0.003). Inverse dose-response associations (with higher BMI related to lower levels) were observed for expression of ER (p=0.01), pan cytokeratin (p=0.004) and four proteins in the p13K/AKT signaling pathway (p ≤ 0.01 for each). Conclusions: Preliminarily, we identify differences in hormonal and immune markers in YBCs in relation to timing of births and BMI, suggesting that these factors may contribute to etiologic heterogeneity. Multivariate modeling is ongoing to incorporate molecular subtype and other risk factors. Citation Format: Robert A. Vierkant, Laura M. Pacheco-Spann, Stacey J. Winham, Jennifer M. Kachergus, Ji Shi, Craig Snow, Fergus J. Couch, Janet E. Olson, Chen Wang, Derek C. Radisky, Amy C. Degnim, E. Aubrey Thompson, Laura C. Collins, Kathryn J. Ruddy, Ann H. Partridge, Mark E. Sherman. Associations of parity and body mass index with NanoString digital spatial protein profiling in early onset breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1000.

Abstract Background: Adjuvant oral tamoxifen (TAM) benefits women with DCIS, but toxicity concerns have limited its acceptance. Transdermal therapy with 4-hydroxy tamoxifen (4-OHT) gel applied to the breast skin is a possible solution. Previous pilot data suggest equivalent anti-proliferative efficacy of TAM and 4-OHT gel, but minimal systemic exposure with transdermal therapy. We report a prospective double blinded randomized phase 2 trial comparing TAM to 4-OHT gel in women with DCIS. Methods: 107 women with estrogen receptor positive (≥10%) DCIS were randomized to TAM (20 mg/day + placebo gel) or 4-OHT gel (2mg 4-OHT gel/breast, bilaterally + oral placebo), for 4-10 weeks prior to surgery. The primary endpoint was reduction in DCIS Ki67 labeling index (LI). Secondary endpoints included the 12-gene DCIS Score assay (Exact Sciences), breast tissue and plasma concentrations of 4-OHT and endoxifen, TAM-responsive circulating proteins, and patient reported symptoms (Breast Eight Symptom Scale). We estimated that 80 evaluable participants would provide 80.5% power to establish non-inferiority of 4-OHT, defined as relative Ki67-LI decline >35% and absolute decline >2.6%, with one-sided 𝛼=0.10. Non-inferiority of 4-OHT gel for Ki67-LI reduction was tested using an ANCOVA model. Statistical comparisons within- and between-arms were calculated with paired t-test and Welch Two Sample t-test, respectively. Results: 72 of 87 women adhered to the protocol, and were evaluable for the primary endpoint (39 TAM and 33 4-OHT gel). Mean treatment duration was 47 days for TAM and 44 days for 4-OHT gel (p=0.2). The median absolute decline in Ki67 labeling index was significant in the oral TAM (-3.7%, p< 0.001) but not in 4-OHT gel arm (-1.3%, p=0.2) (p=0.002). Ki67 results following menopausal stratification also favored the TAM arm: (-1.3%; p=0.06 in 37 premenopausal women and -3.7%; p=0.02 in 35 postmenopausal women). Similarly, DCIS score showed a significantly greater reduction in the TAM (-14, p< 0.001) but not in the 4-OHT gel arm (-4, p=0.1). Tissue 4-OHT concentrations were non-significantly higher in the TAM arm and were similar between superficial and deep sampling locations (superficial 6.1 and 4.2 ng/g for TAM and 4-OHT gel, respectively, p= 0.55; deep 5.7 and 3.8 ng/g, respectively, p= 0.06), whereas plasma 4-OHT concentration was markedly lower in the gel group (2 ng/mL and 0.24 ng/mL for TAM and 4-OHT gel, respectively, P < 0.001). Endoxifen was abundant in plasma (11 ng/mL) and deep tissue (13 ng/g) of the TAM arm, but present in trace amounts in the 4-OHT gel arm (undetectable in plasma and 0.31 ng/g in tissue; p < 0.001). Circulating TAM responsive markers (insulin like growth factor 1, sex hormone binding globulin, von Willebrand factor, and protein S total) and vasomotor symptoms were significantly and unfavorably modulated by TAM, but not by 4-OHT gel therapy. Conclusions: The non-inferiority of transdermal 4-OHT gel to Tam in terms of anti-proliferative effect in DCIS lesions was not demonstrated at the doses used for this study. DCIS Score analysis gave similar results. Tissue 4-OHT concentration in 4-OHT gel and Tam-treated subjects was roughly similar. However, endoxifen exposure was higher with oral TAM therapy and may partially explain the observed differences in major endpoints. In future studies, use of higher 4-OHT gel doses, longer duration of treatment, or different formulation may overcome these. Citation Format: Oukseub Lee, Xinlei Mi, Yanfei Xu, Luis Blanco, Azza M. Akasha, Kelly Benante, Shanshan Zhang, Carissa LaBoy, Thomas Helland, Melissa Pilewskie, Amy Degnim, Zahraa Al-Hilli, Amanda L. Amin, E Shelley Hwang, Joseph M. Guenther, Simon Steinar Hustad, Demirkan B. Gursel, Masha Kocherginsky, Gunnar Mellgren, Eileen Dimond, Marjorie Perloff, Brandy M. Heckman-Stoddard, Seema Khan. PD15-12 A pre-surgical window trial of oral tamoxifen versus transdermal 4-hydroxytamoxifen gel in women with estrogen receptor positive duct carcinoma in situ (DCIS) [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD15-12.

Abstract Nonsteroidal anti-inflammatory agents (NSAID) are associated with modest inconsistent reductions in breast cancer risk in population-based cohorts, whereas two focused studies of patients with benign breast disease (BBD) have found lower risk with NSAID use. Given that BBD includes fibroinflammatory lesions linked to elevated breast cancer risk, we assessed whether NSAID use was associated with lower breast cancer risk among patients with BBD. Participants were postmenopausal women in the Cancer Prevention Study-II (CPS-II), a prospective study of cancer incidence and mortality, who completed follow-up surveys in 1997 with follow-up through June 30, 2015. History of BBD, NSAID use, and covariate data were updated biennially. This analysis included 23,615 patients with BBD and 36,751 patients with non-BBD, including 3,896 incident breast cancers over an average of 12.72 years of follow-up among participants. NSAID use, overall and by formulation, recency, duration, and pills per month was analyzed versus breast cancer risk overall and by BBD status using multivariable-adjusted Cox models; BBD status and NSAID use were modeled as time-dependent exposures. Patients with BBD who reported using NSAIDs experienced lower breast cancer risk (HR, 0.87; 95% CI, 0.78–0.97), with similar effects for estrogen receptor (ER)-positive breast cancers [HR, 0.85; 95% confidence interval (CI), 0.74–0.97] and ER-negative breast cancers (HR, 0.87; 95% CI, 0.59–1.29); among women without BBD, NSAID use was unrelated to risk (HR, 1.02; 95% CI, 0.92–1.13; Pinteraction = 0.04). Associations stratified by age, obesity, menopausal hormone use, and cardiovascular disease were similar. Among patients with BBD, NSAID use appears linked to lower breast cancer risk. Further studies to assess the value of NSAID use among patients with BBD are warranted. Prevention Relevance: We examined whether NSAID use, a modifiable exposure, is associated with breast cancer risk in postmenopausal women from the Cancer Prevention Study-II with self-reported benign breast disease, an often inflammatory condition associated with higher rates of breast cancer.

Abstract Purpose Breast cancer risk is elevated in pathogenic germline BRCA 1/2 mutation carriers due to compromised DNA quality control and elevated mutagenic load. We hypothesized that if immunosurveillance promotes tumor suppression, then normal breast lobules from BRCA carriers may demonstrate higher immune cell densities. Methods We assessed immune cell composition in normal breast lobules from age-matched women with progressively increased breast cancer risk, including 1) 19 women who donated normal breast tissue to the Komen Tissue Bank (KTB) at Indiana University Simon Cancer Center, 2) 15 women with biopsy-identified benign breast disease (BBD), and 3) 19 prophylactic mastectomies from women with germline mutations in BRCA1/2 genes. We performed immunohistochemical stains and analysis to quantitate immune cell densities from digital images in up to 10 representative lobules per sample. Median cell counts per mm2 were compared between groups using Wilcoxon rank-sum tests. Results Compared to BBD tissues, normal breast lobules from BRCA carriers had significantly higher densities of CD8 + cells (median 354.4 vs 200.0 cells/mm2, p = 0.01). Compared to KTB normal donor breast tissues, normal breast lobules from BRCA carriers also had significantly higher densities of CD4+ (median 116.3 vs 17.7 cells/mm2), CD8+ (354.4 vs 150.9 cells/mm2), CD11c+ (3.5% vs 0.4% pixels positive), and CD68+ (237.5 vs 57.8 cells/mm2) immune cells (each p < 0.001). Conclusions These preliminary analyses show that normal/benign breast lobules of BRCA mutation carriers contain increased immune cells compared with BBD and normal donated tissues. Future studies will be helpful to define relationships of mutations and immune responses.

Abstract Background: Biopsy diagnoses of benign breast disease (BBD) confer a 1.5- to 4-fold increased risk of developing breast cancer (BC) compared with women without BBD. Previously, we reported that decreased numbers of specific immune cell types in lobules of BBD biopsies predicted increased BC risk, suggesting the promise of future tissue biomarker studies to define BC risk markers among BBD patients. Thus, we applied protein-based GeoMx® Digital Spatial Profiling (DSP) to BBD biopsies preceding BC (cases) and to BBD biopsies from cancer-free patients (controls) to identify possible BC risk markers, which we then evaluated in subsequent BC tissues and in surrounding normal lobules of cases. Methods: Archived pathology slides of BBD biopsies were reviewed and used to guide preparation of TMAs containing 1.0-mm diameter FFPE cores of lobules from an age- and cohort-period-matched set of 91 cases and 88 controls from the Mayo Clinic BBD Cohort. For patients who later developed BC, we prepared TMAs of BC tissue and surrounding mapped normal lobules. We applied GeoMx® DSP (immune and canonical signaling proteins) to both sets of TMAs. Following QC and data normalization, associations of case status with log-transformed biomarker expression in lobules of BBD biopsies were carried out using linear mixed modeling approaches, accounting for multiple ROIs per individual. Biomarkers significantly associated with case status (p&lt;0.05) were further examined in BCs and adjacent normal lobules, using similar approaches. Results: The mean age at BBD biopsy was 52 years, and at BC diagnosis of cases, 61.4 years (mean time from BBD to BC was 10.2 years). A family history of BC was more frequent among cases (70% versus 43%; chi-square p=0.002). Of 72 biomarkers tested, 46 (64.4%) were evaluable after QC and normalization and 5 were associated with BC risk after adjustment for family history of BC: BCL2 (p=0.005), STING (p=0.006), CD44 (p=0.02), S100 protein (p=0.03) and pan-AKT (p=0.05); each showed higher levels in lobules of BBD biopsies of controls than cases. Three unique patterns appeared when examining these biomarkers across tissue type within cases: for BCL2 (p=5 x 10-9) and STING (p=2 x 10-19), levels were high in both BC and lobules surrounding BC but low in preceding BBD; for GAPDH (p=4 x 10-53) and pan-AKT (p=2 x 10-33), levels were high in BC, low in preceding BBD, and moderate in lobules surrounding BC; and for CD44 (p=2 x 10-6) and S100B (p=2 x 10-49), levels were low in BC, high in lobules surrounding BC and moderate in preceding BBD. Conclusions: Using a novel TMA of lobules in combination with DSP, we preliminarily identified immune-based and PI3 kinase-related protein biomarkers in BBD biopsies associated with BC risk. In case-only analyses, these markers demonstrated complex differences between lobules in BBD biopsies, subsequent BCs and adjacent normal lobules. Citation Format: Robert Alan Vierkant, Jodi M. Carter, Stacey J. Winham, Chen Wang, Jennifer M. Kachergus, Ji Shi, Raymond M. Moore, Bryan M. McCauley, Laura M. Pacheco-Spann, E A. Thompson, Derek C. Radisky, Amy C. Degnim, Mark E. Sherman. Towards prediction of breast cancer risk in benign biopsies with high-plex GeoMx spatial protein profiling [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2203.

Abstract Introduction: The immune microenvironment of the breast is critical in the development and progression of breast cancer. By analyzing the immune components of breast tissues from patients at varying degrees of breast cancer risk, we may gain enhanced understanding of breast cancer risk and mechanisms of carcinogenesis. Methods: We compared the immune cell composition in breast lobules of age-matched patients with normal and benign breast disease (BBD) at progressively lower breast cancer risk: 1) 18 women with germline mutations in (BRCA1/2); 2) women at intermediate risk (BBD), and 3) women at normal risk (Komen Tissue Bank- (KTB)). We performed immunohistochemical stains for T lymphocytes (CD4, CD8); dendritic cells (CD11c); B lymphocytes (CD20) and macrophages (CD68) and quantitated immune cell densities in up to 10 representative lobules per sample. Results: The median age of all groups was 43.8 years (range: 34-67). BRCA carriers and BBD patients had a higher percentage of fibrocystic lobules (50% fibrocystic) compared to KTB samples (15% fibrocystic), p&lt;0.001. BRCA carriers had significantly higher densities of CD4, CD8, CD11c, and CD68 positive immune cells compared to KTB donor breast tissues, see Table. Compared with BBD patients, mutation carriers had higher densities of CD8+ cells and suggestively higher CD4+ cells, with similar results for other markers assessed. Conclusions: Preliminarily, these data showed that benign prophylactic breast tissues from BRCA mutation carriers contain increased numbers of several immune cell types versus tissues from patients at lower breast cancer risk, including BBD patients and research tissue donors. Further investigation is needed to confirm and expand these findings in relation to breast cancer risk. Table: Pairwise Wilcoxon rank-sum p-values comparing immune cell densities in breast lobules from women with BRCA germline mutations, vs BBD and KTB groups. All Lobules BRCA BBD KTB BRCA vs BBD BRCA vs KTB Median Median Median p-value p-value (IQR) (IQR) (IQR) CD4+, cells/mm2 116.3 63.8 17.7 0.08 &lt;0.001 (46.4-183.6) (25.0-121.1) (13.3-40.6) CD8+, cells/mm2 354.4 200 150.9 0.01 &lt;0.001 (285.5-473.2) (118.9-385) (110.1-225.0) CD11c+, % pp 3.5 3.4 0.4 0.66 &lt;0.001 (1.9-6.8) (1.6-4.7) (0-0.6) CD20+, cells/mm2 6.2 16.7 0 0.16 0.65 (0-25.4) (0-58.3) (0-20.8) CD68, cells/mm2 237.5 219 57.8 0.99 &lt;0.001 (122.9-281.8) (75.0-459.4) (29.2-100.0) IQR - Interquartile Range pp - pixel positive Citation Format: Joshua W. Ogony, Tanya L. Hoskin, Melody L. Stallings Mann, Stacey J. Winham, Rushin Brahmbhatt, Muhammad Asad Arshad, Alvaro Pena Jimenez, Teresa M. Allers, Mark E. Sherrman, Daniel W. Visscher, Derek C. Radisky, Amy C. Degnim. Immune biomarkers in breast tissues of patients with BRCA1/2 mutations, benign breast disease, and normal tissue donors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5947.

Abstract Arachidonic acid (AA) metabolizing enzymes, including cyclooxygenases (COX), lipoxygenases, and cytochrome P450s (CYP450), are expressed in breast cancer (BC). Elevated levels of metabolites of COX-derived, pro-inflammatory prostaglandin (PGs) metabolites in urine have been linked to increased risk of developing breast cancer (BC) in two large prospective cohorts. Further, CYP450-derived EETs in BC tumors are associated with metastasis. We hypothesize that measuring levels of AA-derived oxylipins in breast tissues could enable improved BC risk prediction, provide insights into pro-carcinogenic inflammatory mechanisms, and serve as potential surrogate endpoints in chemoprevention trials. Thus, we performed a pilot study to assess the feasibility of measuring these analytes in small breast tissue samples. We analyzed two sample sets, collected under Institutional Review Board (IRB) approved protocols: 50 normal breast tissue cores donated to the Komen Tissue Bank (KTB) via vacuum-assisted biopsy and 10 tissues removed surgically at Mayo Clinic beyond resection margins of lumpectomy samples performed for atypical ductal hyperplasia (ADH). Tissues were frozen and maintained at -80°C. Normal KTB tissue cores were split in half. Tissues for analysis were weighed, extracted in cold methanol containing a cyclooxygenase inhibitor, and assayed for a panel of 42 oxylipins using validated mass spectrometric methods with a limit of detection per analyte of 0.010 ng/mL in supernatant and CVs of approximately &lt;11%. Analyte measurements in paired cores (ng/g tissue) were compared with Spearman correlations and intra-class correlation coefficients. Measurements in surgical samples were assessed descriptively and levels were compared with normal KTB breast tissues.Median weight of the 50 split KTB cores was 0.055 grams. 17 oxylipins were detected in the tissue samples. PGD2 demonstrated the weakest correlation between split cores (r=0.12; p=0.40), whereas 15-HETE demonstrated the strongest correlation (r=0.68; p&lt;0.0001). ICCs ranged from non-significant to nearly perfect, with highest values for 12-HETE (ICC=0.98, 95%CI: 0.97-0.99). Exploratory analyses of the KTB cores demonstrated significant associations between two BC risk factors, alcohol use and family history of breast/ovarian cancer, and several analytes. Levels of most eicosanoids tested were substantially and highly significantly elevated in tissues surrounding ADH versus KTB normal breast tissues. We conclude that eicosanoids can be readily measured in small frozen breast tissue samples obtained via percutaneous biopsy or at surgery. Future studies to assess the associations of eicosanoid levels with BC risk factors and development of BC after a benign biopsy may inform risk prediction and potentially inhibitable inflammatory mechanisms of breast carcinogenesis. Citation Format: Ginger L. Milne, Robert A. Vierkant, Amy C. Degnim, Anna Maria Storniolo, Jill E. Henry, Laura M. Pacheco-Spann, Derek C. Radisky, Mark E. Sherman. Quantification of oxylipins as biomarkers of inflammation and cancer risk in breast tissue [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6333.