Signet ring cell carcinoma of the breast.

A rare case of signet ring cell (SRC) carcinoma of the breast occurring in a 51-year-old female is presented. She was first admitted under the diagnosis of gastric carcinoma. Incidentally, a right breast tumor was detected and double cancer was thus suspected clinically. Concurrent right mastectomy and partial gastrectomy were performed. Histologic examination on the removed tumors revealed infiltration of numerous SRCs. The signet ring appearance of tumor cells resulted from formation of a large intracytoplasmic globule. From this unique cytologic feature along with the presence of in situ lesion in the breast tumor, it was concluded that the gastric malignancy was a sequela of metastasis of infiltrating lobular carcinoma. Wide-spread metastasis later occurred, especially on the serosal surfaces. The importance for the knowledge about the unique metastatic pattern of SRC carcinoma of the breast was emphasized.