Brain Pathology Case of the Month - November 2005

Contributed by Kyle J. Mangels, MD,1 Mahlon D. Johnson, MD, PhD,2 and Robert J. Weil, MD1,3
1Departments of Neurosurgery and
    2Pathology, Vanderbilt University Medical Center, Nashville, TN
    3Brain Tumor Institute, Cleveland Clinic Foundation, Cleveland, OH.


A 35-year-old woman presented with one month's history of progressive bilateral leg weakness and altered sensation. There had been no pain. She had noted urinary frequency and constipation in the previous two weeks. On examination, the patient had diffuse lower extremity weakness (2-3/5), with a T6 sensory level to pain and temperature sensation. Proprioception was preserved. Post-void residuals exhibited urinary retention. There was sacral hypesthesia and decreased rectal tone. She was mildly hyperreflexic (3/4) at the knees and ankles without clonus; both great toes were upgoing. A T1-weighted MRI demonstrated a T4-5 intradural mass ventral to the spinal cord (Fig. 1A), with an enhancing dural tail (Fig. 1B), consistent with meningioma. The lesion was dark on T2-weighted images (Fig. 1C).


At surgery via a posterior, transpedicular approach, an intradural, extramedullary, firm, black neoplasm was encountered, which invaded the ventral dura and elevated and distorted the spinal cord. The mass was removed, leaving only microscopic invasion of the ventral dura (figure 1D, a sagittal MR view, post-contrast, after resection). There was no bone invasion. The tumor fragments measured 2.0x 1.5x 1.0 cm in aggregate. Serial sections revealed a homogeneous black tumor without necrosis. Hematoxylin and eosin stained sections showed an occasionally fascicular tumor of melanocytes and small round blue tumor spindle cells with melanin pigmentation and 1-2 mitotic figures per 10 high-powered fields (Figs. 2 A and 2B). The nuclei are generally oval-shaped and elongated, with prominent nucleoli. Necrosis, hemorrhage, and nuclear and cellular pleomorphism are not present and mitotic figures are rare. MIB-1 labeling (Figs. 3A and 3B) averaged 1-2% in multiple fields. Immunohistochemical staining was positive for S-100 and HMB-45 (Fig. 3C) and S-100 (Fig. 3D).


International Society of Neuropathology