Primary intracranial leiomyoma is an extremely rare occurrence of a low-grade mesenchymal tumor characterized by a proliferation of smooth muscle cells. When present, these lesions predominantly occur in immunocompromised patients in the setting of infection or transplant, and have not been known to involve the ventricular system of the brain. In this report we describe a case of primary leiomyoma of the lateral ventricle in an immunocompetent patient.

A 30-year-old male with no past medical history presented with progressive diplopia and occipital headaches. Magnetic resonance imaging (MRI) of the brain revealed a homogenously enhancing mass of the left lateral ventricle with associated cerebral edema. The patient underwent interhemispheric transcollosal craniotomy for resection for symptom alleviation and surgical diagnosis. Histopathology and immunohistochemistry (IHC) was subsequently consistent with that of leiomyoma. Genetic probing for Epstein-Barr virus was negative. Computed tomography (CT) of the chest and abdomen failed to uncover a primary tumor. The patient did well post-operatively, and was discharged three days following resection. At a two-year and half follow-up, there continued to be no radiological or clinical evidence of recurrence.

Till 2016 there are less than 25 reported cases of primary intracranial leiomyoma, with only 13 occurring in immunocompetent individuals. We believe this is the first report of this tumor type occurring within the ventricular system of the brain. As such, leiomyoma should be considered as a rare etiology in the differential diagnosis of intraventricular lesions ¹⁾.