[Metastasis to the paranasal sinuses from primary breast cancer].

With the symptom diplopia, in addition to an ocular cause, pathology of the paranasal sinuses must always be taken into consideration. A common differential diagnosis is an acute inflammatory process such as an orbital complication of acute sinusitis. We present the rare case of an initial manifestation of metastasis in the paranasal sinuses originating from a primary ductal carcinoma in situ of the breast. In our case, the metastatic manifestation and its clinical symptoms were the first sign of recurrence and transformation into invasive breast cancer.