Angiomatosis of the Breast: Unveiling a Rare and Unusual Vascular Puzzle

Angiomatosis of the breast is a very rare benign vascular lesion that often resembles malignant vascular tumors both clinically and radiologically. Accurate recognition is crucial to avoid misdiagnosis and unnecessary interventions. We report the case of a 35-year-old female who presented with a 20-year history of recurrent, painless enlargement of the left breast. A nipple-sparing mastectomy was performed, and the specimen, measuring 29.5 × 17.5 × 2.5 cm, revealed a diffuse spongy lesion with multiple cystic spaces. Microscopically, the lesion was composed of anastomosing vascular channels of variable caliber surrounding but not invading breast lobules. Immunohistochemistry demonstrated strong nuclear positivity for FLI1 and cytoplasmic positivity for CD31 and CD34, with weak or absent CD34 expression in some vascular spaces. The Ki-67 proliferation index was <2%. These findings suggest the diagnosis of breast angiomatosis. The postoperative recovery was smooth, and no recurrence was observed after four months of follow-up. These cases must be distinguished from low-grade angiosarcoma, which shares overlapping histological features. Features such as the absence of cytologic atypia, a low proliferative index, and supportive immunohistochemical findings help confirm the diagnosis. Complete surgical excision with clear margins is essential, as incomplete excision carries a risk of local recurrence. This report highlights the importance of thorough histopathological and immunohistochemical evaluation in differentiating angiomatosis from malignant vascular tumors of the breast.