Incidental Detection of a Small, Non-spiculated Breast Cancer During Preoperative Evaluation for an Unruptured Cerebral Aneurysm With Gradual Enlargement Over 16 Years: A Case Report.

In older patients with unruptured intracranial aneurysms that have been followed over long periods, careful assessment of operative tolerance and comorbidities becomes an important component of treatment decision-making. Although cross-sectional imaging performed for procedural planning may occasionally reveal extracranial incidental findings, neurosurgical evaluation is typically focused on intracranial pathology. We report a case of an asymptomatic, small, non-spiculated breast cancer incidentally detected during preoperative evaluation for a middle cerebral artery (MCA) aneurysm that had demonstrated gradual enlargement over 16 years. A woman in her 70s was diagnosed with an unruptured cerebral aneurysm at the bifurcation of the right MCA during routine brain screening. Serial magnetic resonance angiography (MRA) demonstrated a gradual increase in aneurysm height, with the development of blebs, prompting surgical intervention. To determine the appropriate treatment strategy, head computed tomography angiography (CTA) was performed. Given the potential for endovascular therapy, whole-body computed tomography (CT) was additionally performed to assess the feasibility of vascular access. This imaging incidentally revealed a 1.0-cm, well-circumscribed, non-spiculated mass in the right breast. Subsequent mammography, ultrasonography, and core needle biopsy confirmed estrogen receptor-positive invasive ductal carcinoma. The aneurysm was treated first with microsurgical clipping, followed by breast-conserving surgery and adjuvant therapy. The postoperative course was uneventful, and no recurrence of either condition was observed at one-year follow-up. In postmenopausal women with aneurysms that gradually enlarge over many years, careful attention to extracranial regions on available imaging becomes particularly important, as clinically relevant disease can arise silently during long-term surveillance. Systematic evaluation of extracranial regions on preoperative imaging may influence both treatment planning and overall patient management.