July 2001: 58-year-old man with a temporal bone mass.

The July 2001 Case of the Month (COM). A 58-year-old man with right ear hearing loss since childhood presented with a two year history of dizziness and vertigo. Neuroradiological studies showed a large mass arising from the petrous portion of the temporal bone. The lesion was resected and microscopic examination revealed a cholesterol granuloma with a small component of cholesteatoma. It is important to distinguish between cholesterol granuloma and cholesteatoma because of treatment differences. However, these two entities can occasionally be seen together and rare giant variants have been described.     

September 2002: 24-year-old female with a 6-month history of seizures

The September 2002 COM. A 24-year-old female presented with a history of 3 generalized seizures, the first of which had occurred 6 months before admission. Her neurological examination was normal, but upon admission her MRI showed a small cystic lesion in the left parieto-occipital region. The lesion was hyper-intense on T-2 weighted images and did not show contrast enhancment. At surgery, the tumor was found to be deep to the cortex and was a cyst with amber fluid surrounded by gliotic brain. Microscopically, the tumor was well-demarcated from the surrounding tissues, which showed reactive changes, including Rosenthal fibers. The tumor was composed of GFAP-positive glial cells, which were arranged in a pseudopapillary fashion around blood vessels. In between, the tumor cells were positive for neuronal markers. The diagnosis was papillary glioneuronal tumor (PGNT), a relatively recently described lesion that may be a variant of ganglioglioma. The current literature on PGNTs is reviewed.     

November 2001: 67-year-old man in coma requiring prolonged mechanical ventilation

A 67-year-old man was found to have massive pituitary necrosis occupying approximately 85% of the anterior lobe after being supported with mechanical ventilation for 35 days. The findings were compatible with "respirator pituitary" found in mechanically ventilated patients. The lesions represent coagulative infarctions due to ischemia. The role of the respirator is believed to be buying time to allow the changes to develop.     

51-year-old woman with double vision

A 51-year-old woman presented with a 2-month history of double vision and numbness around her left ear. She subsequently became unsteady on her feet and developed further cranial nerve abnormalities, before complaining of headache, nausea and vomiting. Imaging revealed features suggestive of two intracranial lesions; one non-contrast-enhancing high-signal area in the cerebellum with associated calcification, and a second contrast-enhancing low-signal area in association with the fourth ventricle, and at surgery there were two apparent components to the tumor. The histopathological features were those of a low-grade, focally calcified tumor comprising atypical ganglion and glial cells with interspersed Rosenthal fibres. Mitotic figures were not seen, and there was no necrosis. An infiltrate of small reactive lymphocytes was interspersed among the neoplastic cells. Immunohistochemistry revealed expression of synaptophysin by many of the dysplastic ganglion cells, with some co-expressing neurofilament protein and occasionally glial fibrillary acidic protein (GFAP). Several of the dysplastic ganglion cells also expressed CD34. The glial cell population was highlighted by GFAP. Ki-67 (MIB-1) activity was not noted among the neoplastic populations--the few positive nuclei in these areas were those of interspersed reactive CD3-positive T lymphocytes. In addition, at the edge of one of the biopsies was a dense infiltrate of mitotically-active large atypical CD 20-positive B lymphocytes, among which the Ki-67 (MIB-1) labeling index reached 80%. The final diagnosis was diffuse large B cell lymphoma arising within a ganglioglioma of the cerebellum, and this is believed to be the first reported case.     

A 61-year-old man with hyponatremia

The case of a 61-year-old man presenting with dizziness, nausea, vomiting, reduced serum osmolality, and hyponatremia is reported. Endocrinologically, low levels for ADH, cortisol and testosterone as well as low-normal values for ACTH, LH and FSH were detected. Cranial computed tomography and MRI scans revealed an intra- and suprasellar tumor of adenoma-like appearance with elevation of the optic chiasm. No infiltration of the cavernous sinus was seen. After transsphenoidal resection of the tumor, no additional anterior lobe insufficiencies or diabetes insipidus occurred. Histological examination revealed a tumor consisting of spindle-shaped cells of uniformly high cellularity with no evidence of hypocellular areas. A cellular schwannoma was diagnosed. An intrasellar cellular schwannoma clinically and radiologically mimicking a non-secreting pituitary adenoma is uncommon. However, rare entities like schwannomas, melanocytomas or pituicytomas have to be considered in addition to the more common tumors like pituitary adenomas and meningiomas.     

February 2003: a 53-year-old male with new onset seizures

The February COM. A 53-year-old obese man presented with new onset seizures and an MRI scan revealed a large cystic and necrotic heterogeneously enhancing left frontal mass. Craniotomy revealed a firm subdural tumor on the cortical surface that was delivered en-bloc preserving the pial planes and stripping it from the falx cerebri. The tumor consisted of multiple irregular fragments of white-tan rubbery tissue admixed with globules of bosselated, white-tan rubbery tissue and a fragment of bone. Sections of the tumor revealed mature hyaline cartilage with no atypia of the chondrocytes. There was focal mineralization and endochondral ossification. A diagnosis of intracranial mesenchymal osteochondroma was made. Osteochondroma, a benign cartilaginous neoplasm comprised of mature hyaline cartilage with focal ossification, is the most common benign bone tumor. Extraskeletal (mesenchymal) osteochondromas are known to originate from non-skeletal or non-cartilaginous tissue. Intracranial osteochondromas are uncommon, typically arising from the base of the skull. Only about 15% of intracranial osteochondromas arise supratentorially, from the dura, usually in a parafalcine frontoparietal location and some have been a component of Maffucci's syndrome and Ollier disease. Intracranial osteochondromas can occur at any age with a predilection for younger individuals. Intracranial mesenchymal osteochondromas exhibit a benign clinical course. Typically, the histomorphology resembles mature hyaline cartilage without anaplastic proliferation of chondrocytes or nuclear atypia, with a lobular arrangement of clusters of lacunae containing single chondrocytes. Transition to osteochondrosarcoma has rarely been documented.     

May 2002: 38-year-old man and 69-year-old woman with dural based masses

The May 2002 COM. A 38-year-old man presented with new onset seizures and a 69-year-old woman presented with bilateral headaches and episodes of syncope. Both were found to have extra-axial masses that were contrast-enhancing and thought to be meningiomas. Both had complete resection. Microscopic examination revealed an inflammatory lesion composed of plasma cells, scattered lymphocytes and numerous large histocytic cells, which exhibited emperi polesis and were CD1 a negative, but positive for CD68 and S100. The diagnosis of Destombes-Rosai-Dorfman Disease (DRDD) was rendered. Both cases had good long-term outcome. The differential diagnosis of inflammatory masses in the dura (plasmacytoma, lymphomas, plasma cell fibroma, angiofollicular hyperplasia [Castleman's-disease] and Langerhan's cell histiocytosis) are discussed.