RT Journal Article SR Electronic T1 Capillary Hemangioma of the Breast Parenchyma Mimicking New Primary Cancer or Metastasis During Ramucirumab Therapy for Advanced Gastric Cancer JF In Vivo JO In Vivo FD International Institute of Anticancer Research SP 545 OP 550 DO 10.21873/invivo.14219 VO 40 IS 1 A1 KIM, HONG-BEUM A1 LEE, YEON-AH A1 KIM, SEONG-HUN A1 PARK, SANG-GON YR 2026 UL http://iv.iiarjournals.org/content/40/1/545.abstract AB Background/Aim: Ramucirumab, a monoclonal antibody targeting vascular endothelial growth factor receptor-2 (VEGFR-2), has been shown to prolong survival in patients with advanced gastric cancer when combined with paclitaxel as second-line chemotherapy in the RAINBOW study. The most common adverse events include hypertension, proteinuria, and hemorrhage, reflecting its anti-angiogenic activity. Although the VEGF signaling pathway is strongly implicated in the pathogenesis of hemangiomas, the development of new hemangiomas during VEGFR-2 inhibition is rarely reported.Case Report: A 38-year-old woman with stage IV gastric adenocarcinoma presented with peritoneal dissemination and lymph node metastasis. She initially received FOLFOX plus immune checkpoint inhibitor therapy, achieving a partial response before disease progression. Second-line treatment with paclitaxel and ramucirumab was initiated. During therapy, chest computed tomography revealed a newly developed contrast-enhancing nodule in the left breast parenchyma, raising suspicion of metastasis or primary breast carcinoma. Breast ultrasonography confirmed a hypervascular lesion, and ultrasound-guided biopsy demonstrated numerous capillary-sized vessels lined by bland endothelial cells, consistent with capillary hemangioma. Owing to deterioration of her general condition, chemotherapy was temporarily discontinued. Despite subsequent third-line FOLFIRI and fourth-line trifluridine/tipiracil treatment, the patient eventually died of disease progression. Notably, follow-up chest CT scans showed gradual reduction and eventual spontaneous disappearance of the breast hemangioma, independent of systemic therapy.Conclusion: This is a rare case of a breast parenchymal capillary hemangioma arising during ramucirumab therapy for advanced gastric cancer, which regressed spontaneously. Clinicians should recognize that atypical vascular lesions may develop paradoxically during VEGFR-2 blockade and confirm histological diagnosis to avoid misinterpretation as metastasis or new primary malignancy.