The patient went on to have surgery. 

Histology

MICROSCOPIC DESCRIPTION:

Paraffin sections show small fragments of a densely hypercellular tumor. Tumor cells have pleomorphic round and oval vesicular nuclei with conspicuous nucleoli and a variable amount of pale cytoplasm. These are arranged in solid aggregates within a vascular stroma. Frequent mitotic figures are identified. Immunohistochemistry shows strong (+++) membrane staining for HER-2 in >90% of tumor cells, strong staining for GCDFP and cytokeratin CK5&6, weak cytoplasmic staining for E-cadherin and weak (+) nuclear staining for estrogen receptor (ER). No staining for progesterone receptor (PgR) is seen in tumor cells.

FINAL DIAGNOSIS: Metastatic undifferentiated carcinoma arising from breast.