The clinical significance and mechanism of DCIS-like morphology of lymph node metastasis in breast cancer.

BACKGROUND

During the practice of diagnostic pathology, we identified a case of invasive ductal carcinoma (IDC) of the breast with lung metastases exhibiting a ductal carcinoma in situ (DCIS)-like morphology. Immunohistochemistry confirmed the presence of CK5/6, P40 and P63-positive tumor cells at the periphery of the metastatic nests. Subsequent expansion of our sample revealed similar DCIS-like morphology in lymph node metastases of other IDC cases. This study aimed to preliminarily characterize the pathological features, significance, and mechanisms of this phenomenon.

METHODS

We collected 101 lymph node metastasis specimens of breast IDC. (1) DCIS-like metastases were identified, and their correlation with clinicopathological parameters was analyzed. (2) Immunohistochemistry for basal/myoepithelial markers (CK5/6, P63, SMA, Calponin) was performed to assess their expression in relation to DCIS-like morphology. (3) Stemness markers (ALDH1A1, CD44, SOX2) were detected, and their expression was correlated with clinicopathological parameters, DCIS-like morphology, and basal/myoepithelial differentiation.

RESULTS

(1) DCIS-like morphology was observed in 24.8% (25/101) of lymph node metastases. Its presence correlated with higher nodal burden and non-luminal molecular subtypes (HER2-enriched and triple-negative). The recurrence rate of the DCIS-like metastasis group was higher than that of the non-DCIS-like metastasis group. (2) A subset of cases showed tumor cell expression of P63, CK5/6, or SMA in metastases, while none expressed Calponin. The proportion of cases expressing basal/myoepithelial markers was higher in the DCIS-like metastasis group, with a significant correlation between DCIS-like morphology and CK5/6 expression. (3) High stemness marker expression correlated significantly with higher histological grade, increased numbers of lymph node metastases, advanced pTNM stage, the presence of DCIS-like morphology, and basal/myoepithelial differentiation.

CONCLUSION

The presence of DCIS-like morphology and basal/myoepithelial marker expression in lymph node metastases of breast IDC is associated with enhanced tumor stemness. DCIS-like metastases may serve as a valuable morphological indicator of higher tumor aggressiveness and increased recurrence risk.