Detection of stromal invasion in breast cancer: The myoepithelial markers

Breast cancer can only be life threatening when it becomes invasive, at whi ch point it carries potential for spreading and metastasis. Therefore, it i s critical to distinguish invasive carcinomas (IC) from noninvasive lesions , the latter including ductal carcinoma in situ (DCIS) and benign breast le sions. While this distinction is usually made based on histologic evaluatio n alone, in a small but significant number of cases, accurate diagnosis may be impossible. particularly in the context of core needle biopsies. To thi s end, a number of immunohistochemical markers have been utilized to help e stablish the presence (or absence) of stromal invasion. The fact that the l oss of the myoepithelial cell (MEC) layer is a hallmark of IC (but not DCIS ) suggests the use of antibodies to MEC to distinguish IC from DCIS. Howeve r, these markers have a wide range of specificity and sensitivity, with the potential for problems in interpretation. The use of many of these markers is limited by high rates of 'false positive' or 'false negative' immunosta ining. In this review, the biology of stromal invasion in breast carcinomas will be discussed, as well as the various myoepithelial markers, with emph asis on pitfalls related to their sensitivity and specificity in the detect ion of MECs in the breast. Finally, the authors will discuss diagnostically challenging breast lesions, which may require the use of MEC marker studie s to reach a definitive diagnosis.