Invasive Ductal Carcinoma of the Left Breast, Stage IV (ER+, PR+, HER2-Negative) with Leptomeningeal Metastasis and Severe Anemia in a Young Woman: A Case Report

Abstract

Breast cancer remains the most prevalent malignancy among women and a leading cause of
global cancer mortality. Although breast cancer in young women (<40 years old) is relatively
rare—accounting for less than 4% of cases in the United States—it often exhibits aggressive
behavior and poor prognosis. Invasive ductal carcinoma (IDC) is the most common histologic
subtype and can metastasize to distant organs, including the central nervous system.
Leptomeningeal metastasis (LM), a rare but devastating complication, occurs more
frequently in hormone receptor-positive, HER2-negative breast cancer. We present a
challenging case of LM in a young woman with recurrent IDC. A 33-year-old woman,
previously diagnosed with IDC (ER+, PR+, HER2−) of the left breast, underwent surgical
resection in 2022, followed by endocrine therapy with tamoxifen and goserelin. In June 2024,
a recurrent mass in the left breast was confirmed malignant by biopsy. In December 2024, she
presented with new-onset diplopia. Laboratory evaluation revealed severe anemia (Hb 6.8
g/dL), mild thrombocytopenia (144 ×10³/μL), elevated transaminases (AST 76 U/L),
hyponatremia (Na 129 mmol/L), and iron studies indicative of inflammation-related anemia
(serum iron 78 μg/dL, transferrin saturation 51%, TIBC 154 μg/dL, ferritin >3000 ng/mL).
BRCA1/2 genetic testing was negative. Chest imaging showed bilateral infiltrates suggestive
of pneumonic-type pulmonary metastases. Bone scans revealed multiple osteolytic lesions in
the scapula, humerus, and clavicle. Contrast-enhanced brain MRI identified a broad-based,
extra-axial, homogeneously enhancing mass in the right medial temporal lobe, consistent
with leptomeningeal involvement. The patient was diagnosed with recurrent IDC, Stage IV,
with LM and bone metastases. Palliative treatment included whole-brain radiotherapy (10 × 3
Gy), high-dose dexamethasone, continued tamoxifen (20 mg/day), and goserelin (3.6 mg SC
monthly). Leptomeningeal metastasis in hormone receptor-positive, HER2-negative breast

cancer is uncommon but represents a serious clinical challenge. This case underscores the
importance of a multidisciplinary and personalized approach in managing advanced breast
cancer with CNS involvement, particularly in young patients.