Classical invasive lobular carcinoma. (A) ILC shows a single file pattern in a dense fibrous stroma with two different cell types. (H & E, ×200) (B) One cell type had a large round vesicular nucleus with a pale eosinophilic cytoplasm. (H & E, ×400) (C) The other cell type had a small hyperchromatic nucleus with dense eosinophilic cytoplasm. (H & E, ×400) (D) Cells with intracytoplasmic lumens resembling signet ring cells. (H & E, ×400).