Tumor-to-Tumor Metastasis Involving Vestibular Schwannoma: Case Report and Literature Review

OBJECTIVE: To present a case of tumor-to-tumor metastasis involving vestibular schwannoma and review previously reported cases, with focus on histopathologic and immunohistochemical characteristics. PATIENTS: Case report of a 55-year-old female with a history of invasive ductal breast carcinoma who presented with unilateral hearing loss and gait disturbance. INTERVENTIONS: MRI demonstrated a right-sided extra-axial cerebellopontine angle lesion. Patient underwent surgical resection with histopathologic and immunohistochemical profiling of the tumor. MAIN OUTCOME MEASURES: A near-total resection was achieved. Microscopic analysis demonstrated vestibular schwannoma with nests of glandular elements. Immunohistochemical staining confirmed metastasis of her known invasive ductal carcinoma to vestibular schwannoma. Subsequent staging imaging showed advanced oncologic spread. CONCLUSIONS: Including the present case, there have been 11 reports of tumor-to-tumor metastasis involving vestibular schwannoma. The risk of tumor-to-tumor metastasis should be considered in patients with concomitant systemic malignancy and vestibular schwannoma. Cell-cell adhesion mechanisms may facilitate the spread of breast cancer to vestibular schwannoma. Further reports may help to better understand vestibular schwannoma by analyzing its interaction with other oncologic entities.