Introduction:Placental metastasis from maternal malignancies is a rare occurrence with a significantly adverse prognosis on the mother with no known effect or established risk factors for the newborn. As such, characterization of these lesions is necessary to serve as a stepping stone for more exhaustive studies regarding this presentation.

Case Summary :This is a case of a metastatic breast carcinoma in a mature singleton placenta in a 39 year old woman diagnosed with invasive breast carcinoma of no special type/invasive ductal carcinoma, not otherwise specified, during the second trimester of pregnancy. Also discussed are the immunohistochemistry studies done to confirm the origin of the tumor. A comparison of the ER, PR, and HER2/neu receptor status between the primary lesion and the placental metastasis was also done.

Conclusion :Pregnancy-associated breast cancer is a lesion that carries adverse prognosis for the mother because of the delay in diagnosis attributable to confusion of symptomatology. The pertinent problem in pregnancy-associated breast cancer with placental metastasis is the deficiency of the placenta to induce tumor metastasis away from itself.