{
  "abstract": "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 (2018–2019). 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: 15–40%). Ki-67 differed significantly between molecular subtypes (Kruskal–Wallis test H = 16.122; p = 0.001; η2 = 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 = −0.65; 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 ρ = 0.035; p = 0.730) or when forced into the retained multivariable model regardless of significance (adjusted b = −0.032; 95% CI: −0.337–0.272; 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.",
  "abstract_shown": true,
  "affiliations": [
    "Faculty of Health Sciences, WSEI University, 20-209 Lublin, Poland",
    "Faculty of Medical and Health Sciences, University of Siedlce, 08-110 Siedlce, Poland",
    "Department of Health Education, Faculty of Nursing Development, Medical University in Lublin, 20-059 Lublin, Poland",
    "Institute of Psychology and Pedagogy, WSEI University, 20-209 Lublin, Poland"
  ],
  "article_type": "research article",
  "arxiv": null,
  "author_total": 5,
  "authors": [
    {
      "affs": [
        0
      ],
      "name": "Dorota Weber"
    },
    {
      "affs": [
        1
      ],
      "name": "Robert Łuczyk",
      "orcid": "0000-0003-0889-6326"
    },
    {
      "affs": [
        2
      ],
      "name": "Anna Pacian"
    },
    {
      "affs": [
        0
      ],
      "name": "Teresa Kulik"
    },
    {
      "affs": [
        3
      ],
      "name": "Monika Baryła-Matejczuk",
      "orcid": "0000-0003-2321-9999"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/cqsr2bbkkg7za.bib",
  "cited_by": 0,
  "doi": "10.3390/ijms27198797",
  "fulltext_url": "https://europepmc.org/articles/PMC13665338",
  "id": "cqsr2bbkkg7za",
  "issns": [
    "1422-0067"
  ],
  "landing_url": "https://www.mdpi.com/1422-0067/27/19/8797",
  "language": "eng",
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "openalex",
      "1306|Breast Cancer Treatment Studies"
    ]
  ],
  "openalex": "W7215118867",
  "pdf_url": "https://europepmc.org/articles/PMC13665338?pdf=render",
  "pmcid": "PMC13665338",
  "pmid": "42884041",
  "published": "2026-10-01",
  "publisher": "MDPI AG",
  "ris": "https://research.draconitic.com/paper/cqsr2bbkkg7za.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:18:55Z",
      "native_id": "10.3390/ijms27198797",
      "source": "crossref",
      "url": "https://www.mdpi.com/1422-0067/27/19/8797"
    },
    {
      "first_seen": "2026-10-30T12:19:00Z",
      "native_id": "MED:42884041",
      "source": "europepmc",
      "url": "https://europepmc.org/article/MED/42884041"
    }
  ],
  "subjects": [
    {
      "field": "medicine",
      "origin": "openalex:1306|Breast Cancer Treatment Studies",
      "subfield": "oncology"
    }
  ],
  "title": "Molecular Proliferation Marker Ki-67 in Breast Cancer: The Role of Vitamin D Status, Hormone Receptor Expression, and Clinicopathological Factors—A Cross-Sectional Study",
  "title_text": "Molecular Proliferation Marker Ki-67 in Breast Cancer: The Role of Vitamin D Status, Hormone Receptor Expression, and Clinicopathological Factors—A Cross-Sectional Study",
  "type": "peer-reviewed",
  "updated_at": "2026-10-30T12:19:00Z",
  "url": "https://research.draconitic.com/paper/cqsr2bbkkg7za",
  "venue": "International Journal of Molecular Sciences",
  "versions": []
}