Stage IV ER-positive/HER2-negative breast cancer with synchronous gastric and bone metastases

What happened, in summary

This 78-year-old woman sought care for chronic belching, dyspepsia, daily nausea, intermittent melena, vomiting, and post-meal epigastric pain. She had never undergone screening mammography and had no known family history of breast or colorectal cancer. Endoscopy showed erosive mucosal change along the lesser curvature of the stomach and a small peripyloric opening, and biopsy of that subtle gastric abnormality revealed metastatic carcinoma favoring a breast primary. Immunohistochemistry in the gastric biopsy showed an invasive lobular pattern with strong ER positivity at 95%, PR negativity below 1%, HER2 0, and E-cadherin loss. Mammography and ultrasound then found a right breast lesion with right axillary lymphadenopathy. CT showed diffuse mixed osteolytic and sclerotic lesions throughout the axial and appendicular skeleton, consistent with widespread bone metastases. The right breast core biopsy showed grade 2 invasive ductal carcinoma, ER 91-100%, PR 91-100%, HER2 0, and Ki-67 5%. A right axillary lymph-node fine-needle aspiration was positive for malignancy. Together, the findings supported newly diagnosed metastatic breast cancer with a ductal breast primary and gastric metastasis showing lobular features, likely reflecting tumor heterogeneity. She began palliative systemic treatment with anastrozole plus the CDK4/6 inhibitor palbociclib for hormone receptor-positive, HER2-negative metastatic disease. Proton pump inhibitor therapy also helped her upper-GI symptoms. At 2-month follow-up, CT imaging was similar to baseline, with persistent diffuse bone metastases but no early radiographic worsening. She continued to tolerate endocrine and CDK4/6 therapy, and no additional follow-up was available beyond that early stable period. The early result therefore supported disease control and symptom improvement, while still reflecting ongoing Stage IV breast cancer requiring palliative systemic treatment.