Background <p>The tumour microenvironment and systemic inflammatory environment are related to the diagnosis, treatment and prognosis of various tumours. This study aimed to evaluate the clinicopathological significance and prognostic value of the tumour microenvironment and systemic environment in patients with breast invasive ductal carcinoma (IDC).</p> Methods <p>A total of 222 patients with breast IDC who underwent radical mastectomy were included. Stromal maturity and tumour-infiltrating lymphocytes (TILs), along with a series of systemic inflammatory cell indicators from venous blood, were evaluated. Chi-square tests were performed to explore the relationships between the parameters. Kaplan‒Meier analysis and Cox proportional hazards regression models were used for survival analysis.</p> Results <p>Stromal maturity was significantly correlated with tumour necrosis, lymphovascular invasion, axillary lymph node metastasis, and clinical stage (all <i>P</i> &lt; 0.001). TILs were significantly associated with nuclear grade, histopathological grade, tumour necrosis, lymphovascular invasion, and clinical stage (all <i>P</i> &lt; 0.001). High TIL numbers were often accompanied by more mature stroma. No significant correlations were detected between stromal maturity/TILs and systemic inflammatory markers. Multivariate Cox proportional hazards model analysis revealed that TILs, pathological grade, clinical stage, and molecular subtype were independent prognostic factors for patients with IDC. ROC curve analysis revealed that the accuracy of stromal maturity detection was greater than that of TILs alone, and the combined assessment of both parameters achieved the best predictive performance.</p> Conclusions <p>Stromal maturity and TILs in patients with breast IDC have important clinicopathological and prognostic significance, providing clinical guidance and a theoretical basis for the precise diagnosis and prognostic evaluation of this disease.</p>