Review links intramammary lymph node metastasis with axillary involvement in primary breast cancer

A systematic review and meta-analysis found that pathologically confirmed intramammary lymph node metastasis was strongly associated with axillary lymph node involvement among women with primary breast cancer. The pooled analysis included 24 studies involving 1,482 patients and reported an odds ratio of 4.96 (95% confidence interval, 3.55–6.93) for the association between intramammary lymph node positivity and axillary lymph node involvement.

The review, summarized in a Scientific Reports abstract, examined the incidence and metastatic rate of intramammary lymph nodes, their diagnostic performance, associated risk factors and prognostic findings. The pooled incidence of pathologically detected intramammary lymph nodes was 0.03 (95% confidence interval, 0.01–0.08), while the pooled metastatic rate was 0.32 (95% confidence interval, 0.27–0.37). The abstract did not specify the denominator underlying the reported metastatic rate, so it should not be interpreted as a rate for the entire study population.

For diagnostic performance, the meta-analysis reported pooled sensitivity of 0.505, specificity of 0.813, positive predictive value of 0.674 and negative predictive value of 0.711. It also reported a positive likelihood ratio of 2.738, a negative likelihood ratio of 0.635 and a diagnostic odds ratio of 4.961. These pooled indices describe the overall performance reported across the included studies rather than the performance in an individual patient. The authors concluded that the diagnostic accuracy of intramammary lymph node metastasis was insufficient to replace standard axillary staging.

Pooled analyses also identified lymphovascular invasion, tumor size or T stage, and histological grade as factors commonly associated with intramammary lymph node metastasis. Prognostic findings were inconsistent across the evidence, and the review reported that the independent prognostic value of intramammary lymph node metastasis remained inconclusive. The review therefore supports a strong association with axillary involvement but does not establish a uniform independent effect on patient outcomes. The available evidence is limited to the study-level results presented in the abstract, and the conclusion is based on 24 studies with a combined population of 1,482 patients.

Subject of Research: Systematic review of intramammary lymph node metastasis and axillary involvement in women with primary breast cancer

Article Title: Clinical significance of intramammary lymph nodes in female primary breast cancer: a systematic review and meta-analysis

Article References: Zhao, Z., Wang, X., Zhang, W., Zhang, L., Pei, S., Yang, Y., Qu, Z., Li, Z., Lu, J., Fang, Y., Wang, J., & Wang, Z. (2026). Clinical significance of intramammary lymph nodes in female primary breast cancer: a systematic review and meta-analysis. Scientific Reports. https://doi.org/10.1038/s41598-026-70289-9

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DOI: 10.1038/s41598-026-70289-9

Keywords: primary breast cancer, intramammary lymph nodes, axillary metastasis, systematic review, meta-analysis, diagnostic accuracy, lymphovascular invasion, prognosis, Clinical, significance, intramammary, lymph