Molecular Features and Organotropism in Metastatic Breast Cancer : A Comparison of the Skull and Brain

Abstract

  Metastatic breast cancer tends to occur 5 or more years after the initial treatment of primary tumors. Neurosurgeons often treat breast cancer as skull or brain metastasis. However, the clinical and molecular features of skull and brain metastases of breast cancer remain unclear. To identify these characteristics, we retrospectively investigated data from patients with skull or brain metastasis of breast cancer treated at our hospital (skull metastasis, three cases ; brain metastasis, eight cases). We focused on the latency until recurrence, expression patterns of the estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2), and Ki-67 index in each sample. Our results showed that ER/PR-positive and HER2-negative patients had skull metastasis with long latency (average : 13.7 years ; range : 8-17 years), whereas ER/PR-negative and HER2-positive patients had brain metastasis presenting earlier relapse compared with skull metastasis (average : 3.8 years ; range : 1-6 years). The Ki-67 index was significantly lower in skull metastasis than in brain metastasis (average Ki-67 index of skull metastasis : 8% [range : 3-16%] ; brain metastasis : 38% [range : 17-50%] ; p＜0.05). Our results suggested that skull and brain metastases in breast cancer have distinct molecular characteristics.