{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,1]],"date-time":"2026-10-01T10:58:14Z","timestamp":1790852294377,"version":"4.1.0"},"reference-count":31,"publisher":"MDPI AG","issue":"19","license":[{"start":{"date-parts":[[2026,10,1]],"date-time":"2026-10-01T00:00:00Z","timestamp":1790812800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Int. J. Mol. Sci.","IJMS"],"abstract":"<jats:p>Ki-67 is a well-established nuclear biomarker of tumor cell proliferation with key importance for the molecular classification and prognostic stratification of breast cancer. This cross-sectional study included 101 women with histopathologically confirmed invasive breast cancer treated at the St. John of Dukla Oncology Center of the Lublin Region (COZL), Poland (2018\u20132019). Ki-67 expression was assessed immunohistochemically on formalin-fixed, paraffin-embedded tumor tissue, and independent predictors were identified using multiple linear regression. The median Ki-67 was 20% (IQR: 15\u201340%). Ki-67 differed significantly between molecular subtypes (Kruskal\u2013Wallis test H = 16.122; p = 0.001; \u03b72 = 0.138): Luminal A tumors had the lowest Ki-67 (median 18%), whereas the Luminal B, HER2-enriched, and Triple-negative subtypes showed higher values (median 30% each). Ki-67 was significantly lower in tumors expressing the estrogen receptor (p = 0.005) and progesterone receptor (p = 0.023). Because the Luminal A\/B distinction incorporates a Ki-67 threshold by definition, a multivariable model excluding molecular subtype was fitted using ER, PR, HER2, menopausal status, age, BMI category, and 25(OH)D as candidate predictors. This model identified HER2 positivity (b = 11.26; p = 0.024) and postmenopausal status (b = 17.93; p = 0.017) as independent predictors of higher Ki-67, with a borderline inverse association for age (b = \u22120.65; p = 0.092); the model explained 10.1% of variance (R2 = 0.101; F(3,95) = 3.574; p = 0.017), and neither ER, PR, BMI, nor 25(OH)D were retained. Serum 25(OH)D concentration showed no meaningful association with Ki-67, either unadjusted (Spearman \u03c1 = 0.035; p = 0.730) or when forced into the retained multivariable model regardless of significance (adjusted b = \u22120.032; 95% CI: \u22120.337\u20130.272; p = 0.834); no association was observed between circulating 25(OH)D and Ki-67 in this cohort, although indirect biological relationships cannot be excluded.<\/jats:p>","DOI":"10.3390\/ijms27198797","type":"journal-article","created":{"date-parts":[[2026,10,1]],"date-time":"2026-10-01T10:25:44Z","timestamp":1790850344000},"page":"8797","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Molecular Proliferation Marker Ki-67 in Breast Cancer: The Role of Vitamin D Status, Hormone Receptor Expression, and Clinicopathological Factors\u2014A Cross-Sectional Study"],"prefix":"10.3390","volume":"27","author":[{"given":"Dorota","family":"Weber","sequence":"first","affiliation":[{"name":"Faculty of Health Sciences, WSEI University, 20-209 Lublin, Poland"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"methodology","vocabulary":"credit"},{"role":"formal-analysis","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"},{"role":"data-curation","vocabulary":"credit"},{"role":"writing-original-draft","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"},{"role":"visualization","vocabulary":"credit"},{"role":"supervision","vocabulary":"credit"},{"role":"project-administration","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0889-6326","authenticated-orcid":false,"given":"Robert","family":"\u0141uczyk","sequence":"additional","affiliation":[{"name":"Faculty of Medical and Health Sciences, University of Siedlce, 08-110 Siedlce, Poland"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"formal-analysis","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"},{"role":"writing-original-draft","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"}]},{"given":"Anna","family":"Pacian","sequence":"additional","affiliation":[{"name":"Department of Health Education, Faculty of Nursing Development, Medical University in Lublin, 20-059 Lublin, Poland"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"formal-analysis","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"},{"role":"resources","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"}]},{"given":"Teresa","family":"Kulik","sequence":"additional","affiliation":[{"name":"Faculty of Health Sciences, WSEI University, 20-209 Lublin, Poland"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"methodology","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2321-9999","authenticated-orcid":false,"given":"Monika","family":"Bary\u0142a-Matejczuk","sequence":"additional","affiliation":[{"name":"Institute of Psychology and Pedagogy, WSEI University, 20-209 Lublin, Poland"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"formal-analysis","vocabulary":"credit"},{"role":"data-curation","vocabulary":"credit"},{"role":"writing-original-draft","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"}]}],"member":"1968","published-online":{"date-parts":[[2026,10,1]]},"reference":[{"key":"ref_1","first-page":"209","article-title":"Global Cancer Statistics 2020: GLOBOCAN Estimates of Incidence and Mortality Worldwide for 36 Cancers in 185 Countries","volume":"71","author":"Sung","year":"2021","journal-title":"CA Cancer J. 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