Identification of a Subtype of Poorly Differentiated Invasive Ductal Carcinoma of the Breast Based on Vimentin and E-cadherin Expression

Objective The use of molecular markers can identify a subgroup of tumors with distinct recurrence patterns. The present study aimed to characterize the immunohistochemical expression of vimentin (VIM), of E-cadherin (CDH1), and of cytokeratin 5 (CK5) in patients with invasive ductal carcinomas (IDCs). Methods We have constructed a tissue microarray (TMA) from 87 patients with IDC of the breast. Immunohistochemistry (IHC) was performed to study the expression of estrogen and progesterone receptors (ER and PgR), human epidermal growth factor receptor 2 (HER2), VIM, CDH1, CK5, and Ki67. The tumors were classified as luminal A and B (n = 39), HER2 enriched (n = 25), and triple-negative (TNBC) (n = 23), based on the IHC expression. Results We have observed that luminal A and B tumors lack the VIM(+)/CDH1(-/low) phenotype. This phenotype was observed in 16.5% of the HER2+ tumors and in 60% of the TNBC tumors (p = 0.0001). Out of a total of 20 TNBC tumors, the CK5 (basal-like marker) was positive in 11 of them. The VIM(+)/CDH1(-/low) phenotype was observed in 5 CK5+ TNBC tumors (45%) and in 7 out of 9 CK5- TNBC tumors (78%) (p = 0.02). The median Ki67 index in the VIM(+)/CDH1(-/low) tumors was 13.6 (range: 17.8–45.4) compared with 9.8 (range: 4.1–38.1) in other tumors (p = 0.0007). The presence of lymph node metastasis was less frequent in patients with VIM(+)/CDH1(-/low) tumors (23% versus 61%; X(2) test; p = 0.01). Conclusion Our findings suggest that the expression of VIM and CDH1 can identify a subset of IDCs of the breast with a mesenchymal phenotype associated with poor prognosis, high-grade lesion, and high mitotic index.