Metastatic Mucinous Adenocarcinoma Presenting as Cerebellopontine Angle Tumor

Intracranial posterior fosse metastasis is a common entity. Metastatic mucinous adenocarcinoma presenting as cerebellopontine angle (CPA) tumor is very rare. The authors presented a 47-year-old female patient with right CPA tumor. The magnetic resonance imaging brain showed a heterogeneous contrast-enhancing ducal-based extra-axial right CPA lesion involving the right cerebellar hemisphere, internal auditory meatus, and posterior surface of the right petrous bone. The patient underwent surgery, and subtotal resection of the tumor was done. Histology of the tumor was metastasis from a mucinous adenocarcinoma. Contrast-enhanced computed tomography scan of the abdomen and pelvis, ultrasound of the thyroid, chest X-ray, and thyroid function tests were normal. Carbohydrate antigen (CA) 19-9 was 949.37 TJ/mL, serum carcinoembryonic antigen (CEA) was 48.17 ng/mL, and CA-125 was 8.20 U/mL. In view of the raised CA 19-9 and CEA, primary malignancy was believed to be arising from the pancreas or from the gastrointestinal tract, though the definitive diagnosis of primary malignancy was not made. Although rare, metastatic mucinous adenocarcinoma should be kept in the differential diagnosis of CPA lesions. Even though the tumor is radiologically mimicking as CPA schwannoma, the absence of hearing abnormality should raise the suspicion for other diagnoses.