Cerebellopontine angle metastasis of a neuroendocrine tumor mimicking vestibular schwannoma: A case report

Abstract

Background: Neuroendocrine tumors (NETs) are uncommon neoplasms arising from neuroendocrine cells and are rarely associated with intracranial metastases.

Case description: We discuss the case of a 74-year-old woman with a right CPA tumor. She had a history of retroperitoneal NET, but was diagnosed with vestibular schwannoma due to a right-sided hearing loss and a right CPA tumor along the VII and VIII nerves. After a 3-year follow-up, she presented with repetitive vomiting, a 1-month history of gait instability, and a 3-month history of general fatigue. Brain imaging revealed tumor growth and edematous changes in the right cerebellum. She underwent retrosigmoid craniotomy and partial resection. Histopathological examination revealed metastatic NET. She underwent stereotactic radiosurgery for residual lesion and, at 11 months of follow-up, the lesion was confirmed to have shrunk on magnetic resonance imaging (MRI).

Conclusion: This is the first case to report the natural course of cerebellopontine metastasis of a NET. The differential diagnosis of CPA tumors is diverse, and, in our case, we suspected a vestibular schwannoma because of the typical symptoms and imaging features. However, the tumor grew relatively faster than expected and showed intratumoral hemorrhage during the 3-year follow-up. Therefore, in patients with a history of a NET, a careful follow-up is advisable even for lesions highly suspected to be another benign tumor on MRI. Careful follow-up imaging and appropriate treatment strategies were useful to manage the brain metastasis. Although NETs metastasizing to the CPA are extremely rare, this possibility should be considered when patients with NETs have intracranial lesions.

Keywords: Brain metastasis; Case report; Cerebellopontine angle tumor; Neuroendocrine tumor; Neuroendocrine tumors; Vestibular schwannoma.

Figure 1:

Contrast-enhanced magnetic resonance imaging (CE-MRI) findings of the cerebellopontine angle lesion. (a) Images taken on the first consultation showed a suspicious lesion of about 12 mm in size, resembling a vestibular schwannoma, at the right cerebellopontine angle. (b) CE-MRI images 2 years after the first consultation (13 months before admission) showed no change in the tumor size. (c) CE-MRI images taken 7 months before admission showed an intratumoral cyst and tumor growth to 20 mm. (d) CE-MRI taken 1 month before admission showed intratumoral hemorrhage, edematous changes in the right cerebellum, and tumor growth to 27 mm.

Figure 2:

Imaging findings on the day of admission. Computed tomography scan (a), contrast-enhanced magnetic resonance imaging (CE-MRI) (b), and fluid-attenuated inversion recovery (c) images on the day of admission showing the tumor (arrow), hemorrhage (arrowhead), and extensive edematous changes in the right cerebellum. CE-MRI (d) showed the enlargement of lateral ventricles.

Figure 3:

Histological findings indicating metastatic neuroendocrine tumors. Hematoxylin and eosin staining showed monotonous tumor cells with round nuclei and eosinophilic cytoplasm arranged in nested or trabecular pattern (a). Immunohistochemically, tumor cells were positive for cytokeratin (b), synaptophysin (c), and CD56 (d), although they were negative for chromogranin A (e). Ki-67 labeling index was 5.7% (f).

Figure 4:

Postoperative imaging findings. Contrast-enhanced magnetic resonance imaging on the next day after the surgery (a and b) showing partial resection of the tumor. T1-weighted MRI 11 months after surgery (c and d) showing a reduction in the size of the residual lesions.