Malignant Transformation of Recurrent Residual Cerebellopontine Angle Epidermoid Tumor: Significance of Clinical Vigilance and Long-Term Surveillance

Abstract

Epidermoid tumors (ET) are slow-growing masses where malignant transformations occur extremely rarely. Malignant transformation warning signs are the rapid-onset, progression, and recurrence of symptoms. The radiologic evidence for malignant transformation is contrast enhancement with rapid growth, observed with magnetic resonance imaging (MRI) or computed tomography scans. Here, we provide a case report of a 68-year-old woman with a long-standing history of left-sided cerebellopontine angle ET who presented with a recent worsening of symptoms, and MRI observation of new ET contrast enhancement. Surgical re-exploration and histopathologic confirmation are mandatory in this setting of recent symptom worsening and MRI observation of rapid mass growth.

Keywords: brain tumor; cerebellopontine angle; epidermoid tumor; malignant transformation; rapid progression; recurrence; squamous cell carcinoma.

Fig. 1

Presurgical magnetic resonance imaging (MRI). ( A, B ) Axial T2-weighted MRI with a predominantly hypointense 2.3 × 1.9 × 1.9 cm solid mass in the left dorsal midbrain, and left-sided hyperintense 4.2 × 3.8 × 3.2 cm cerebellar cystic mass. Axial ( C, D ) and coronal ( E , F ) MRI show a heterogeneous rim-enhancing mass in the left dorsal midbrain and pons with nonenhancing cerebellar mass. ( G , H ) Axial diffusion-weighted images show cerebellar cystic mass with diffusion restriction, and nonrestricted mass in the left dorsal midbrain.

Fig. 2

Immediate postsurgery magnetic resonance imaging (MRI). ( A, B ) Axial T2-weighted MRI. Axial ( C, D ) and coronal ( E, F ) MRI and axial diffusion-weighted imaging ( G, H ) revealed microsurgical gross total resection of both components of the mass.

Fig. 3

Forty-five days postsurgery magnetic resonance imaging (MRI). ( A, B ) Axial T2-weighted MRI. Axial ( C, D ) and coronal ( E, F ) MRI and axial diffusion-weighted imaging ( G, H ) revealed a large recurrent heterogeneous rim-enhancing mass within the dorsal left midbrain measuring 3.1 × 2.3 × 2.3 cm, with resultant mass effect on the cerebral aqueduct and inferior third ventricle.

Fig. 4

Immediate post second surgery magnetic resonance imaging (MRI). ( A, B ) Axial T2-weighted MRI. Axial ( C, D ) and coronal ( E, F ) MRI and axial diffusion-weighted imaging ( G, H ) revealed subtotal 90% resection of malignant squamous transformation of the midbrain epidermoid tumor.

Fig. 5

( A ) At low magnification, infiltration of gliotic central nervous system marked with * is evident by finger-like projections of squamous cell carcinoma (arrows; hematoxylin and eosin stain, original magnification 4x). ( B ) At higher magnification, malignant squamous cell is recognized by their abundant pink cytoplasm, atypical nuclei, enlarged nucleoli, and presence of atypical mitotic activity (arrows; (hematoxylin and eosin stain, original magnification 10x).