59 Year Old Female with Cerebellopontine Angle Hemorrhage

Clinical History

A 59 year old female with a history of hypertension presented with a one week history of nausea, bloody vomiting, and vertigo. After resolution of her nausea with antiemetic medication, she opted to return the following morning for an upper gastrointestinal endoscopy. That evening she developed sudden neurologic decline. EMS intubated her on the scene. At the Emergency Department, she was following commands in all four extremities but demonstrated anisocoria with ophthalmoplegia and left facial weakness.

Admission laboratory and clotting studies were unremarkable. Non‐contrast CT of the brain demonstrated acute hemorrhage with fullness near the internal acoustic meatus (IAM) (Figure 1a). CT angiography was negative.

Figure 1.

 

An MRI demonstrated a 2.2 × 2.2 × 2 cm left CPA mass with extension into the IAM with surrounding hemorrhage (Figure 1b). In total, the lesion with surrounding hemorrhage was approximately 3.5 × 3.7 × 3.4 cm in size. The working diagnosis was hemorrhagic vestibular schwannoma. The CPA hematoma was evacuated, revealing a soft, hemorrhagic and easily suckable CPA mass near the IAM. Subtotal resection of the mass was performed. The patient emerged from surgery in good condition but required tracheostomy due to lower cranial neuropathies. After a full discussion with the patient and her family regarding her diagnosis, the patient elected to be discharged to home for hospice care on hospital day 9.

Microscopic Pathology

This neoplasm was composed of highly pleomorphic and mitotically active spindle cells. Focal individual cells had hypereosinophilic cytoplasm. (Figure 1c). The tumor was focally immunoreactive for S‐100 protein (Figure 1d) as well as desmin (Figure 1e) and myogenin (Figure 1f), while being negative for EMA, cytokeratin (AE1/3), and neurofilament protein. What is your diagnosis?

Diagnosis

High grade malignant peripheral nerve sheath tumor with rhabdomyosarcomatous differentiation, also called “Malignant triton tumor”.

Discussion

The differential diagnosis of a cerebellopontine angle tumor should always begin with a vestibular schwannoma which account for 80% of tumors at this location. Vestibular schwannomas, however, are rarely associated with hemorrhage. In contrast, intratumoral hemorrhage within a malignant peripheral nerve sheath tumor (MPNST) is not uncommon and in fact may be used a sign of malignant transformation of an otherwise benign nerve sheath tumor1. Meningiomas and epidermoid cysts constitute the majority of the remaining tumors at this location.

Intracranial malignant Triton tumors are exceedingly rare, and only 5 other reports of cerebellopontine angle MTTs are reported in the literature2. The term “Triton” tumor is derived by an observational association with experiments of Triton salamanders in which the implantation of a nerve could result in growth of a limb containing skeletal muscle. Thus, a Triton tumor is a neoplasm containing neural and skeletal muscle elements. A malignant Triton tumor (MTT) specifically refers to a malignant peripheral nerve sheath tumor with rhabdomyosarcomatous differentiation, a sarcoma subtype first described in by Masson 1932.

MTTs have a similar patient demographic to that of classic MPNST with a mean age in the thirties and without gender predilection 2, 3. A significant proportion of MTTs arise in the setting of neurofibromatosis 1, with reports ranging from 38–57%3, 4. Previous radiation exposure has also been cited as a risk factor1, 3.

Proper diagnosis is essential as MTTs typically follow a more aggressive clinical course than their MPNST counterparts. A recent series established that the overall 5‐year survival for MTT is 14%, compared to MPNST of 34%3. With metastases not uncommon, with a cited rate of 31%, surgical excision followed by radiotherapy is the recommended therapeutic approach 3.