Thrombospondin-1 is highly expressed in desmoplastic components of invasive ductal carcinoma of the breast and associated with lymph node metastasis.

Desmoplastic (scirrhous) invasion and lymph node metastasis are critical for the treatment and prognosis of invasive ductal carcinoma of the breast. Despite being an anti-angiogenic therapeutic candidate, Thrombospondin-1 (TSP-1) promotes invasion and metastasis of some carcinomas. To clarify the effect of TSP-1 on invasion and metastasis, we obtained 101 invasive ductal carcinomas of the breast with axillary lymph node resection. All tumors were histologically divided into two categories, carcinomas with, and those with non- /minimal desmoplastic component. Immunohistochemistry for TSP-1 was performed on all primary tumors and axillary lymph nodes with tumor metastasis. Fifty-four (53.5%) of 101 tumors were recognized as positive for TSP-1 in the cytoplasm of tumor cells. Histological study showed that significantly more cancers with desmoplastic components (46/69, 66.7%) manifested TSP-1 expression than did cancers with no- or minimal (less than 20%) desmoplasia (8/32, 25.0%; p<0.001). Axillary lymph node metastasis was significantly higher in TSP-1-positive- (28/54, 51.9%) than TSP-1-negative cancers (11/47, 23.4%; p<0.005). The present study indicates that tumor cells in the desmoplastic component strongly expressed TSP-1 in invasive ductal carcinoma of the breast and TSP-1 participates in invasion of these tumors. Our findings also suggest that TSP-1 promotes lymph node metastasis and TSP-1 potentially could be a predictive marker for metastasis.