What happened, in summary

This 38-year-old woman presented in December 2022 with abdominal distension and discomfort. Endoscopy and abdominal CT showed Stage IV gastric carcinoma with peritoneal dissemination and preaortic lymph-node involvement. Pathology confirmed poorly differentiated adenocarcinoma. Biomarker testing showed HER2-negative disease, PD-L1 tumor proportion score of at least 5%, intact mismatch repair proteins, microsatellite stability, and no actionable mutations on next-generation sequencing. She first received FOLFOX plus nivolumab. After 4 cycles, imaging showed a partial response, and that response was maintained across 13 cycles. The disease later progressed, with CT showing peritoneal thickening and omental caking. Second-line paclitaxel plus ramucirumab was started, leading to symptom relief and radiographic shrinkage of the peritoneal disease within 2 months. Around that time, chest CT unexpectedly showed a new contrast-enhancing 1 cm nodule beneath the left areola. Because a new breast lesion in a patient with advanced cancer could represent metastasis or a second primary breast cancer, ultrasound-guided biopsy was performed. Pathology showed a benign capillary hemangioma: numerous small vessels in fibrous stroma, lined by bland endothelial cells without atypia or mitotic activity. The gastric cancer remained the serious active problem. She stopped chemotherapy for about 2 months because of worsening performance status, and later CT showed renewed peritoneal progression while the breast nodule became smaller. Third-line FOLFIRI was given for 3 cycles and briefly improved abdominal symptoms, but the cancer progressed to massive ascites. Fourth-line trifluridine/tipiracil was attempted. On final chest CT, the breast nodule had completely disappeared. She ultimately died from rapid gastric-cancer progression.