The presence of micropapillary features and retraction artifact in core needle biopsy material predicts lymph node metastasis in breast carcinoma.

Retraction artifact around tumor cell nests is a characteristic feature of invasive micropapillary carcinoma (IMPC), a special type of breast cancer commonly associated with nodal metastasis. We have recently reported that the extent of retraction artifact in usual invasive ductal carcinomas (IDC) is also a strong predictor of nodal metastasis. We examined whether the presence and extent of micropapillary features and retraction artifact in core needle biopsy of breast cancers can predict nodal metastasis in a prospective series of 47 IMPC and 424 IDC. Micropapillary features were present on core needle biopsy in 28 of 47 IMPC cases. Nodal metastases were found in 21 of 28 and 14 of 19 IMPC cases with and without micropapillary features present on core needle biopsy, respectively. Lymph node metastasis was significantly associated with the presence of micropapillary features, but not with its extent within these tumors. The presence of extensive retraction artifact in core needle biopsy samples of IDC also showed a significant association with nodal metastasis. Our results indicate that the presence of micropapillary features or extensive retraction artifact on core needle biopsy of breast carcinoma can predict nodal metastasis. Our results support the notion that the characteristic clear spaces separating the tumor cells from the stroma in IMPC and IDC of the breast are not a random artifactual phenomenon simply resulting from tissue fixation and processing, but rather they are likely related to altered tumor-stromal interactions, which might have an important role in lymphatic tumor spread.