It is a very good practical case!!

印戒细胞癌. Most likely a gastric primary. However, for cases like this one: 46 years old female, a probability of metastatic lobular carcinoma of the breast is the major differential diagnosis. These two disease, particularly in small biopsy, show a great deal of overlapping histological features. I routinely do a panel of IHC to distingish them. Each year, I experience 3 or 4 metastatic lobular carcinoma to the stomach. Some metastatic lobular carcinomas first presented as a gastric mass, and follow-up studies found the primary breast cancer.