Objective: Myoepithelial carcinoma of the breast is an extremely rare tumor, composed purely of myoepithelial cells, predominantly spindle, with identifiable mitotic activity. Method: We report a case of a 50 year-old female patient with a palpable, well demarcated lump in her left breast, measuring 3,5 cm in its maximal diameter. Surgical excision and axillary lymph node dissection were performed. Results: Histologically, the tumor displayed an infiltrating growth pattern and consisted of spindle cells, that appear to emanate from myoepithelial cells of ductules entrapped in the center of the lesion. Mitotic activity did not exceed 5 mitotic figures/10 HPF. Immunohistochemically, the tumor cells revealed positivity for p63, cytokeratin 5/6, cytokeratin 34βΕ12, smooth muscle actin, CD10 and S100 protein, whereas they were negative for desmin, cytokeratin 7, CD34, HMB45, estrogen, progesterone receptors and Her-2 oncoprotein. Approximatelly 25 % of tumor cells showed nuclear positivity for MIB-1/Ki-67. All axillary lymph nodes were free of metastases. Conclusion: Myoepithelial carcinoma of the breast is a potentially highly aggressive neoplasm and its differential diagnosis is fairly broad, including metaplastic spindle cell carcinoma and a variety of myofibroblastic lesions. Objective: We investigated the differential expression of several biological markers between primary invasive breast carcinomas and their paired lymph node metastasis analyzing separately epithelial and stromal components. Method: Representative samples of 42 IDC and paired compromised lymph nodes were arrayed in a TMA and 15 selected markers: hormonal receptors, HER-1, proliferation (p53, pAKT, pmTOR, TGFβ1) , motility (CD9 and CXCR) and basal markers (CK5, CK14, c-kit) were evaluated by IC. Results: In the primary tumor, p53, MIB-1, TGFβ1, CD9 and CXCR4 were more expressed in epithelial cells (p< 0.05), while pAKT, pmTOR, c-myc and c-kit showed a similar frequency in both components. Hormone receptors, HER-1/HER-2 and cytokeratins were not expressed in stromal cells. The proliferative biomarkers were concordant in the epithelial component. CD9 frequency was similar but cytoplasmic CXCR4 as opposite to nuclear was predominantly expressed in lymph nodes (p=0.008). Stromal cells from lymph node showed a reduced frequency of CD9 (p= 0.029) and c-myc (p=0.003) when compared to the stromal component of primary tumors. Conclusion: Epithelial CXCR4 expression may facilitate lymph node metastasis whereas the low frequency of cmyc and CD9 in the lymph node stromal component indicated decreased proliferation enhanced motility of stromal cells in this site.