Intramedullary Tumors

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Chapter 7 Intramedullary Tumors

Jae-Soo Koh, Ung-Kyu Chang, Terri Haddix

1 Astrocytoma
2 Ependymoma
3 Capillary Hemangioblastoma
4 Spinal Cord Cavernous Angioma
5 Ganglioglioma
6 Neurocytic Tumors
7 Oligodendroglioma
8 Embryonal Neoplasms
9 Spinal Cord Intramedullary Metastasis

INTRAMEDULLARY TUMORS

Spinal cord intramedullary tumors are mostly benign. Primary intramedullary tumors originate from glial cell, neuronal cell, or other connective tissue cells. Glial tumors are astrocytoma, ependymoma, and oligodendroglioma. Astrocytomas are neoplasms of astrocytic origin within the spinal cord which demonstrate immunoreactivity for glial origin cells. They infiltrate into the surrounding spinal cord tissue, which makes radical resection difficult. Ependymomas, another glial tumor, are from the ependymal lining cells of the central canal in the spinal cord. They rarely show infiltrative growth pattern. Oligodendrogliomas are composed of proliferations of neoplastic oligodendroglial cells.

Intramedullary tumors from vascular tissue are hemangioblastomas and cavernous angiomas. Spinal cord hemangioblastomas are vascular neoplasms of benign nature that occur sporadically or in association with von Hippel–Lindau (VHL) disease. They are usually attached to the pial surface. Cavernous angiomas are composed of thin-walled, dilated, abnormal, vascular channels without neural tissue.

Tumors of neuronal components are gangliogliomas, neurocytomas, and embryonal neoplasms. Gangliogliomas are composed of both glial and neuronal neoplastic cells. The glial component is typically piloid to fibrillary, and a dysplastic neuronal portion also is identified.

Embryonal neoplasms correspond to primitive neuroectodermal tumors (PNETs), and neurocytic tumors are matched with central neurocytomas in the brain.

Metastatic lesions are rarely seen in the spinal cord and result from vascular rather than subarachnoid spread.

ASTROCYTOMA

EPIDEMIOLOGY

• Intramedullary spinal cord astrocytomas represent 6–8% of spinal cord tumors.1
• In the pediatric population this tumor is the most common glial neoplasm and is typically low grade.2
• In adults, astrocytomas are the second most common glial spinal cord neoplasm after ependymomas.
• Pilocytic astrocytomas of the spinal cord are associated with neurofibromatosis type 1 (NF-1).

DISTRIBUTION

• Astrocytomas may involve any region of the spinal cord, although the cervical area is most commonly affected in children.2
• Holocord involvement may occur.

HISTOLOGY/GRADING

General

• These tumors are composed of neoplastic astrocytes that demonstrate immunoreactivity for glial fibrillary acidic protein (GFAP).
• GFAP immunoreactivity may be lost in some high-grade astrocytomas (e.g., glioblastomas and gliosarcomas).

Pilocytic Astrocytoma (Grade I)

• The classic histologic phenotype is of a biphasic neoplasm composed of looser (and cystic) areas with protoplasmic astrocytes and densely cellular areas composed of hair-like (piloid) cells (Fig. 7-1).
• Eosinophilic granular bodies (Fig. 7-2) are more commonly found in loose areas, whereas Rosenthal fibers (Fig. 7-3) predominate in densely cellular areas.
• Oligodendroglial-like cells (cells with rounded nuclei and perinuclear clearing) may be prominent in some regions (Fig. 7-4).
• Pilocytic astrocytomas (PAs) are associated with NF-1.
• The histologic differential includes gliosis (particularly when only densely cellular areas are sampled) and rarely occurring oligodendrogliomas or other tumors with clear cell histology (e.g., ependymoma).
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Fig. 7-1 Classic histologic appearance of pilocytic astrocytoma (hematoxylin–eosin stain, ×200).

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Fig. 7-2 Eosinophilic granular body in a less cellular area of a pilocytic astrocytoma (hematoxylin–eosin stain, ×400).

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Fig. 7-3 Rosenthal fibers in a densely cellular area of a pilocytic astrocytoma (hematoxylin–eosin stain, ×200).

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Fig. 7-4 A prominent oligodendroglial-like phenotype in one area of a pilocytic astrocytoma (hematoxylin–eosin stain, ×200).

Diffuse Astrocytoma (Grade II)

• This neoplasm shows relatively low cellularity and is composed of cells with angulated nuclei and modest nuclear pleomorphism (Fig. 7-5).
• The neoplastic astrocytes may have varied appearances, including fibrillary or gemistocytic (plump).
• Low mitotic activity without evidence of microvascular proliferation or pseudopalisading necrosis is characteristic.
• The histologic differential includes ganglioglioma if infiltrated gray matter is sampled. The presence of a population of clearly dysplastic ganglion cells should be sought to make the diagnosis of ganglioglioma.
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Fig. 7-5 A fibrillary astrocytoma infiltrating gray matter. Note the neurons with large nuclei and prominent nucleoli in the left upper and center fields of the figure (hematoxylin–eosin stain, ×200).

Anaplastic Astrocytoma (Grade III)

• The histologic features are similar to the grade II tumors just described, but with the presence of increasing cellularity and mitotic activity.
• No microvascular proliferation or pseudopalisading necrosis is seen.

Glioblastoma (Grade IV)

• Features of anaplastic astrocytoma (Fig. 7-6) with microvascular proliferation and/or pseudopalisading necrosis (Fig. 7-7).
• Leptomeningeal seeding may occur with higher grade astrocytomas.
• Occasionally true sarcomatous differentiation may be found (gliosarcoma), but these tumors typically involve the cerebral hemispheres.
• Small cell glioblastoma may be confused with an anaplastic oligodendroglioma. Cytogenetic analyses may help distinguish these tumors. Many oligodendrogliomas demonstrate deletions of the short and long arms of chromosome 1 (1p) and chromosome 19 (19q), respectively, and amplification of the epidermal growth factor receptor gene is found in some small cell glioblastomas.
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Fig. 7-6 Cytologic features of increased cellularity and mitotic figures shared by grades III and IV astrocytomas (hematoxylin–eosin stain, ×400).

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Fig. 7-7 The presence of pseudopalisading necrosis (upper center) and/or microvascular proliferation (lower two-thirds) distinguish grade IV from grade III astrocytomas (hematoxylin–eosin stain, ×100).

RADIOLOGY

• Magnetic resonance imaging (MRI) shows enlargement of the cord at the tumor location.
• Astrocytoma shows slightly low signal or iso-intensity relative to the cord on T1-weighted images (T1WI) and high signal on T2-weighted images T2WI) (Fig. 7-8).
• After injection of intravenous gadolinium, no enhancement of the intramedullary mass is noted. Syringomyelia and hemorrhage are not found.
• Reactive or neoplastic cysts are identified in high-grade glioma.3
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Fig. 7-8 MRI showing diffusely widened spinal cord extending from C1 to C5 in low-grade astrocytoma. Sagittal T2WI (left) shows high signal intensity, sagittal T1WI (center) low signal intensity, and enhanced image (right) a slightly enhanced lesion.

EPENDYMOMA

EPIDEMIOLOGY

• In the pediatric population, ependymomas are nearly always intracranial in location.
• The peak incidence of spinal ependymomas is in the fourth and fifth decades of life.1
• Spinal intramedullary ependymoma arises from the central canal and accounts for 1.5–3% of central nervous system (CNS) tumors.
• Ependymoma accounts for 15% of all spinal cord tumors, comprises 60% of spinal gliomas, and is known to be the most common intramedullary spinal cord tumor in adults.

DISTRIBUTION

• Ependymomas may be found at any region of the spinal cord, although cervical and cervicothoracic segments are slightly more favored.
• Myxopapillary ependymomas have a predilection for the filum terminale and conus medullaris.

HISTOLOGY/GRADING

Most spinal ependymomas are histologically benign and rarely show infiltrative growth. Though they do not form tumor capsules, the interface between the tumor mass and the surrounding normal cord tissue is relatively well defined.4

General

Ependymomas demonstrate cytoplasmic GFAP immunoreactivity. Both punctate intracytoplasmic and ring-like epithelial membrane antigen (EMA) immunoreactivity have been reported in ependymomas.5,6

Myxopapillary Ependymoma (Grade I) (Fig. 7-9)

• These tumors demonstrate a papillary architecture composed of vessels covered by a layer of monomorphic cells and separated by pools of mucin.
• An eosinophilic aggregate is often seen within the mucin.
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Fig. 7-9 The classic histologic appearance of a myxopapillary ependymoma (hematoxylin–eosin stain, ×200).

Ependymoma (WHO Grade II)

• This grade of ependymoma is composed of monomorphic cells with little mitotic activity.
• The cells often aggregate with processes extending to centrally positioned vessels forming perivascular pseudorosettes (Fig. 7-10).
• True ependymal rosettes (tumor cells aligned to form a true central lumen) are uncommon.
• Microvascular proliferation and sheet-like growth patterns are not found to an appreciable degree.
• Histologic variants include clear cell, tanycytic, and papillary.
• Areas of calcification and hyalinization may be found.
• Depending on the degree of sampling, the histologic differential can include other clear cell neoplasms (e.g., oligodendroglioma) and other papillary neoplasms (e.g., choroid plexus lesions), all of which should be distinguishable based on their immunohistochemical profiles.
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Fig. 7-10 Perivascular pseudorosettes are prominent in this example of a grade II ependymoma (hematoxylin–eosin stain, ×200).

Ependymoma (Grade III)

High-grade ependymomas demonstrate greater cellularity, a sheet-like growth pattern, increasing mitotic activity, nuclear anaplasia, and microvascular proliferation, as compared with grade II neoplasms. It may be difficult in some circumstances to distinguish high-grade ependymomas from grade IV astrocytomas.

RADIOLOGY

• Spinal intramedullary ependymoma usually shows low-signal intensity on T1WI and high-signal intensity on T2WI MRI (Figs. 7-11 and 7-12).
• It has good contrast enhancement and a well-demarcated margin, but the signal intensity and the degree of enhancement are variable because of the different distributions of the vascular component of the connective tissue in the tumor mass (Figs. 7-13 to 7-15).7
• Homogeneous enhancement is observed in 47% of tumors and heterogeneous enhancement in 53%. In most cases, the interface between the tumor and the spinal cord is clearly identified.
• Associated syrinx is commonly seen in intramedullary ependymomas. It is known that tumor syrinx occurs in more than 50% of cases of intramedullary ependymomas, which is greater than the incidence of syrinx in spinal astrocytomas.
• The more proximally located the tumor mass, the more often tumor syrinx tends to develop.8
• Syrinx is more commonly found on the cephalic side of the tumor mass than on the caudal side and at the cervical level rather than the thoracolumbar level. These tendencies suggest that the development of the syrinx may be related to the cerebrospinal fluid circulation.9
• The presence of syrinx in intramedullary spinal cord tumors is known to be a good prognostic factor because it enables complete resection of the tumor mass with the provision of an excellent dissection margin between the tumor mass and normal cord tissue.
• A tumor cyst is found in 43% of cases. Low-signal intensity on T2WI suggests repeated hemorrhage.
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Fig. 7-11 T2 sagittal MR of myxopapillary ependymoma at conus level. High signal mass is encroaching the L1 vertebral body. In the tumor mass, serpentine structures (feeding vessels) are seen.

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Fig. 7-12 T1 sagittal MR of myxopapillary ependymoma. The mass signal is isointense to the spinal cord.

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Fig. 7-13 With gadolinium use, the mass shows bright enhancement.

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Fig. 7-14 On the axial view at the L1 vertebral body level, intradural mass is extending to posterior portion of the vertebral body.

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Fig. 7-15 Enhanced axial view at L1. The intradural mass has bright enhancement, and dural ectasia is seen along the posterior vertebral body.

CAPILLARY HEMANGIOBLASTOMA

EPIDEMIOLOGY

• Spinal cord hemangioblastoma is an uncommon vascular neoplasm of a benign nature.
• It can occur throughout the CNS and is a rare disease entity. It accounts for 1.6–6.4% of all spinal cord tumors, 3.3–14.8% of intramedullary tumors, and 13% of all hemangioblastomas.
• This tumor predominates in young males and usually has an intramedullary location.10
• The association with VHL disease, a multicentric disorder of autosomal dominance with an incomplete penetrance, is well recognized and occurs in 20–30% of patients.11
• Three-fourths of these tumors occur sporadically.
• Capillary hemangioblastoma (CH) affects men and women equally and is most often detected in adults.
• The mean age of symptom onset is the fourth decade of life.11

DISTRIBUTION

• Approximately one-third of CNS CH is found in the spinal cord.
• CHs have a predilection for the thoracic cord, where approximately 50% are found. Another approximately one-third are identified in the cervical segment.
• Intramedullary location is the most common.

HISTOLOGY/GRADING

• Tumors are located on the dorsal or dorsolateral surface of the spinal cord, so conventional midline myelotomy is not required for the exposure.
• The neoplasm with dilated vessels is identified. The feeding artery is manipulated before the draining vein.
• CHs are highly vascular tumors with a propensity for hemorrhage. In addition to vessels, the tumors are composed of vacuolated stromal cells (Fig. 7-16, A).
• The stromal cells are not immunoreactive for vascular markers (e.g., CD31 and CD34) or glial markers (e.g., GFAP).
• The stromal cells are immunoreactive for the alpha subunit of inhibin (Fig. 7-16, B). This pattern of immunoreactivity helps distinguish CH from metastatic renal cell carcinoma.
• The histologic differential includes metastatic renal cell carcinoma (clear cell phenotype), which is also one of the manifestations of VHL disease.
• Hemangioblastomas are grade I neoplasms.
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Fig. 7-16 Hemangioblastoma. A, Vacuolated stromal cells separated by a rich vascular network (hematoxylin–eosin stain, ×200). B, Inhibin immunoreactivity (brown staining) in the stromal cells. Note the lack of immunoreactivity in the vasculature (×400).

RADIOLOGY

• On the MR image, the signal of the mass is isointense to the spinal cord on T1WI and hyperintense on T2WI (Figs. 7-17 and 7-18).
• The tumor mass itself shows as a brightly enhanced nodule. Tumor syrinx is associated, and peritumoral edema is usually present (see Fig. 7-17).
• The enhancing nodules are located subpially on the posterior aspect of the spinal cord (Figs. 7-19 to 7-22).
• There is a strong tendency for the tumor to be associated with cyst formation (in approximately 50–70% of cases).
• Spinal cord ependymoma has similar patterns of enhancement and associated syrinx in MR findings. However, it shows no vascular markings in MRI and does not demonstrate any tumor vessels on angiography.
• Spinal cord vascular malformation can be misdiagnosed as CH because of its high vascularity and widespread surrounding edema. However, spinal cord vascular malformation is rarely accompanied by a syrinx, and tumor enhancement is not present on MRI.11
• When the patient has VHL disease, multiple angiomas can be associated. These are cerebellar hemangioblastoma; retinal angioma; pheochromocytoma; renal cell carcinoma; and angiomatous lesion of the kidney, pancreas, and epididymis (Figs. 7-23 to 7-25).
• Spinal angiographic findings of the feeding artery and the draining vein are essential for surgical planning.
• On spinal angiography the mass shows intense, prolonged vascular stain with or without arteriovenous shunting (Fig. 7-26).
• Enlarged spinal arteries may be seen to supply the mass.
• Differential diagnosis should be considered with spinal cord ependymoma and vascular malformation.
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Fig. 7-17 T2 sagittal view of C7 hemangioblastoma. Intramedullary syrinx cavity is seen from the C5 to T2 level. The mass is not shown.

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Fig. 7-18 T1 sagittal view of C7 hemangioblastoma. The mass is invisible because the size is so small and isointense signal with the spinal cord.

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Fig. 7-19 Enhanced MR of C7 hemangioblastoma. Small subpial nodule is seen on the posterior surface of the spinal cord. It is well-demarcated, intense, homogeneously enhanced.

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Fig. 7-20 On axial view, the enhanced nodule is located on the right posterior surface of the spinal cord.

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Fig. 7-21 Thorcolumbar spine MR of the same patient in Figure 7-20. At T11 level, another enhancing nodule is found. The enhancing pattern is similar. The patient is a 26-year-old female diagnosed with VHL disease.

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Fig. 7-22 Axial image at T11. The enhancing nodule is adherent to the conus at the right side.

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Fig. 7-23 Abdominal CT of the same patient. Small highly enhancing nodule is found in the pancreas tail, suggestive of angioma (small arrow). Two small cysts, less than 10 mm, are found in the left kidney (large arrow).

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Fig. 7-24 Abdominal CT of the same patient in Fig. 7-23. A 17-mm highly enhancing solid mass, related to renal cell carcinoma, is found in the right kidney.

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Fig. 7-25 Brain MR of the same patient in Figs. 7-23 and 7-24. Cystic hemangioblastoma is seen at the right cerebellopontine angle, and multiple small nodules are found on the cerebellar surface.

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Fig. 7-26 Angiography of another C2 hemangioblastoma. Hypervascular mass is fed by the right posterior inferior cerebellar artery on right vertebral angiography.

SPINAL CORD CAVERNOUS ANGIOMA

EPIDEMIOLOGY

• Cavernous angiomas are vascular malformations that may localize in any part of the CNS. In the spinal cord, cavernous angiomas may be extradural, extramedullary-intradural, or intramedullary.
• Sexual predilection is reported to be nearly equal between males and females. However, the risk of hemorrhage is greater in females because of hormonal effect.
• The third to fourth decades of life are the most affected, although no age group is exempt.

DISTRIBUTION

• The true incidence of spinal cord cavernous angioma (SCCA) is unknown. It represents 5–12% of all spinal vascular abnormalities,12 comprising 5% of all spinal intramedullary lesions in adults and 1% in children.
• Incidence of the multiple forms of cavernous angioma seems to be greater in patients with intramedullary cavernous angioma. Incidence of the multiple forms is reported to be at least 25%.13
• In the spinal cord the lesion may be situated posteriorly and bulge on the surface; however, it also may be entirely buried in the spinal parenchyma so that it is not visible on the surface. The overlying parenchyma may show yellowish discoloration because of the presence of hemosiderin.

HISTOLOGY

• SCCA is composed of thin-walled, dilated, abnormal vascular channels (Fig. 7-27).
• The thrombus is filled in the vascular structures. There is no neural tissue between the vascular channels. Fibrous proliferation is observed in some of the vessel walls.
• Elastic fiber or smooth muscular tissue is absent in the vascular walls. Hemosiderin and hemosiderin laden macrophages are observed on the periphery of the lesion with gliosis.
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Fig. 7-27 Cavernous angioma shows abnormal vascular channel. There is no neural tissue in the intervening area (hematoxylin–eosin stain, ×40).

RADIOLOGY

• MRI is the diagnostic modality of choice; spinal angiography shows negative results. MRI findings depend on the stage of hemorrhage within the lesion.
• The typical MRI appearance is a well-defined lesion that is composed of hypointense areas intermixed with small punctate areas of hyperintensity on both T1WI and T2WI (Fig. 7-28).14
• SCCAs are generally surrounded by a hypointense hemosiderin ring on T2WI (Fig. 7-29).
• SCCAs are enhanced variably.
• There typically is no signal void that is characteristically seen in high flow vascular lesions.15
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Fig. 7-28 Sagittal (A, B, and C) and axial (D) MRI scans. A, T2-weighted MR image demonstrating an intramedullary small lesion at the C5 level with surrounding edema. B, T1-weighted MR image. C, T1-weighted MR image after intravenous administration of gadolinium reveals no enhancement of mass. D, T2-weighted axial MR image demonstrating an intramedullary mass at the left side of the spinal cord.

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Fig. 7-29 T2-weighted sagittal image. Intramedullary round mass surrounded by a hypointense hemosiderin ring at the C2 level.

GANGLIOGLIOMA

EPIDEMIOLOGY

• Gangliogliomas are unusual CNS tumors. They are rarely found in the spinal cord; the rate of incidence is reported to be 1.1% of all spinal cord neoplasms.16
• However, some authors report an incident of up to 14%, making ganglioglioma the second most common intramedullary tumor after astrocytomas in patients younger than 10 years.17,18
• This neoplasm is much more common in pediatric than in adult populations. The incidence declines with age; only a few cases have been reported beyond the fourth decade of life.19

DISTRIBUTION

• This tumor most commonly involves the cervical spinal cord, often with involvement of the caudal brainstem or thoracic cord.17,19
• Holocord involvement may occur.

HISTOLOGY/GRADING

• General

• The histologic features of ganglioglioma may be found in association with other neoplasms (e.g., pilocytic astrocytoma or pleomorphic xanthoastrocytoma).
• With subsequent resections, one component only (e.g., glial) may be evident.

• This tumor is composed of both glial and neuronal components. The glial component is typically piloid to fibrillary in appearance (Fig. 7-30). Identification of a dysplastic neuronal component (e.g., clusters of large, atypical, binucleate neurons) is essential for the diagnosis (Fig. 7-31).
• Eosinophilic granular bodies may be present.
• Perivascular lymphocytic infiltrates are common.
• These tumors correspond to histologic grades I–III depending on the degree of anaplasia and mitotic activity in the glial portion of the tumor.
• The histologic differential includes a low-grade astrocytoma infiltrating normal gray matter (previously discussed), which imparts the importance of identifying a population of truly dysplastic neurons.
• Operative finding: The masses are mainly solid with some cystic portions that are thought to be a syrinx cavity. A dissection plane exists in some parts with good demarcation from normal cord tissue by both consistency and color, but in some parts tumor infiltration is suspected because of the irregular margin. The tumors are not so much hypervascular, and the masses can be removed without difficulty.16
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Fig. 7-30 Ganglioglioma demonstrating both glial and neuronal components. Note the presence of perivascular lymphocytic infiltrates (upper left), a commonly identified feature of ganglioglioma (hematoxylin–eosin stain, ×200).

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Fig. 7-31 Dysplastic neurons in a ganglioglioma (hematoxylin–eosin stain, ×400).

RADIOLOGY

• Radiologic features of intramedullary spinal cord ganglioglioma are nonspecific.
• On MRI, the mass shows high signal intensity on T2WI and slightly high to iso-signal intensity on T1WI (Fig. 7-32).
• Heterogeneous strong enhancement of the mass with a relatively well-demarcated margin is observed.
• Syrinx is usually accompanied by the tumor mass. A syrinx cavity is not easily distinguishable from a cystic portion of the tumor on MRI. Tumor cysts usually do not show as low a signal as cerebrospinal fluid.20 An irregular margin, associated soft tissue components, and enhancement with gadolinium help distinguish a cyst from a syrinx.20
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Fig. 7-32 MR of cervical ganglioma. A, On T2WI, a high signal intensity mass is seen with a syringomyelia from C1–6. B, A homogeneously enhanced mass is seen at the C1 level.

NEUROCYTIC TUMORS

EPIDEMIOLOGY

This group includes:

• Glioneuronal tumors with rosetted islands (GTRI), a recently described, rare neoplasm primarily involving the cerebral hemispheres,21 with scattered case reports involving the spinal cord.22
• Central neurocytomas that typically involve the cerebral hemispheres and rarely the spinal cord.23

DISTRIBUTION

The thoracic spine has been the predominant site of involvement by these tumors in case reports.

HISTOLOGY/GRADING

• Central neurocytomas and GTRIs are composed of small, round, uniform synaptophysin-immunoreactive cells with neuropil islands (Figs. 7-33 and 7-34).
• GTRIs also have a subpopulation of GFAP immunoreactive cells (Fig. 7-35).
• Pure neurocytic neoplasms are classified as grade II lesions.
• The glioneuronal tumors have not been formally graded in the most recent World Health Organization classification system. However, based on the clinical behavior of the cases reported in the literature, a grade of II–III is warranted.24
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Fig. 7-33 Relatively acellular areas and cystic areas in a GTRI (hematoxylin–eosin stain, ×200).

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Fig. 7-34 Synaptophysin immunoreactivity (brown reaction product) within acellular areas in a GTRI (×200).

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Fig. 7-35 Subpopulation of GFAP immunoreactive (brown staining) cells in a GTRI (×200).

OLIGODENDROGLIOMA

EPIDEMIOLOGY

• Oligodendrogliomas of the spinal cord are very rare, with approximately 50 total reported in the literature.25
• This tumor is reported more frequently in adult than in pediatric populations.

DISTRIBUTION

This tumor may occur in all regions of the spinal cord, but the cervical and thoracic levels are involved most often.

HISTOLOGY/GRADING

• These neoplasms are composed of proliferations of neoplastic oligodendroglial cells.
• The classic histologic features of these neoplasms are round nuclei, a vesicular chromatin pattern, and a perinuclear halo (the latter is a fixation artifact imparting the so-called “fried egg” appearance).
• In the spinal cord, oligodendroglial-like cells are more likely to represent a component of another glial neoplasm (e.g., pilocytic astrocytoma or ependymoma) than a primary oligodendroglioma.

Grade II

• Low-to-moderate cellularity and rare mitotic figures are seen.
• No vascular proliferation or necrosis is found.

Grade III (Fig. 7-36)

• Although the classic oligodendroglial histologic features are often found, the cells demonstrate increased nuclear membrane irregularities, greater cellularity, and increased proliferation indices as compared with grade II neoplasms.
• Vascular proliferation and pseudopalisading necrosis are found.
• The histologic differential includes small cell glioblastoma, as discussed earlier.
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Fig. 7-36 Anaplastic oligodendroglioma demonstrating classic histologic “fried egg” appearance and areas of vascular proliferation (hematoxylin–eosin stain, ×100).

EMBRYONAL NEOPLASMS

EPIDEMIOLOGY

Primary primitive neuroectodermal tumors (PNETs) of the spinal cord are exceptionally rare, with approximately 20 reported cases.26

DISTRIBUTION

• Supratentorial PNETs and other embryonal tumors (e.g., medulloblastoma, pineoblastoma, or atypical teratoid/rhabdoid tumors) may disseminate and involve the spinal cord at any level.
• These spinal implants from disseminated disease are usually not biopsied, but are followed radiographically and/or through cerebrospinal fluid sampling (Fig. 7-37).
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Fig. 7-37 Cytospin preparation of cerebrospinal fluid containing aggregates of embryonal cells in a patient with a previously diagnosed medulloblastoma and radiographic evidence of dissemination (Papanicolaou stain, ×600).

HISTOLOGY/GRADING

• The embryonal neoplastic cells are small with high nuclear-to-cytoplasmic ratios. The exception is atypical teratoid/rhabdoid tumors in which rhabdoid morphology (moderate amount of eosinophilic cytoplasm with an eccentrically positioned nucleus) is found.
• Mitotic activity and nuclear molding are readily identifiable.
• Architectural features of the primary neoplasm (e.g., Homer Wright rosettes in medulloblastoma) may be present (Fig. 7-38).
• The immunophenotype varies depending on the nature of the primary neoplasm; diffuse synaptophysin immunoreactivity is reported in medulloblastomas.
• All embryonal tumors are classified as grade IV neoplasms.
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Fig. 7-38 Medulloblastoma composed of small cells with little cytoplasm and nuclear molding. Homer Wright rosettes are easily identified. (hematoxylin–eosin stain, ×400).

SPINAL CORD INTRAMEDULLARY METASTASIS

EPIDEMIOLOGY

• Spinal cord intramedullary metastasis (IM metastasis) is reported in 1–3% of all intramedullary cord tumors, with 140 cases reported to date.
• The primary cancers that cause IM metastasis are lung cancer, breast cancer, melanoma, lymphoma, and renal cell carcinoma. Half of the lung cancers that cause IM metastasis are small cell lung cancer.
• The pathogenetic mechanism for IM metastasis is arterial embolization. The theoretical basis for arterial embolization is that the most common primary cancer is lung cancer. Lung cancer metastasis usually occurs via arterial spread, not via venous channel. IM metastasis is often associated with brain metastasis; leptomeningeal metastasis is not accompanied by IM metastasis.

DISTRIBUTION

• The most commonly involved segment is the cervical cord, which is a vascular rich area. The involvement of conus is the least common.
• The size of the mass is typically small (<1.5 cm).
• The morphology is well-circumscribed and spherical.
• Clinical characteristics of the IM metastasis are rapid onset and rapid progression of motor weakness. But in epidural metastasis, the initial presentation is pain, and motor weakness follows.
• Expected survival in cases of IM metastasis in lung cancer is 4–5 months.

RADIOLOGY

• The radiologic clue for IM metastasis is focal, enhancing the cord lesion with extensive surrounding edema.
• On T2WI, a high signal lesion is identified and the surrounding cord edema is definite (Fig. 7-39).
• On T1WI, the mass is not delineated. Generalized cord swelling is only observed (Fig. 7-40).
• With gadolinium use, a small spherical mass is seen with bright contrast (Figs. 7-41 and 7-42).
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Fig. 7-39 T2-weighted sagittal MR of intramedullary metastasis of colon cancer. Focal, high signal, round lesion is seen at the T3 vertebral level. Associated cord edema has developed around the lesion.

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Fig. 7-40 T1-weighted sagittal MR of intramedullary metastasis of colon cancer. The mass is isointense to the spinal cord. It is invisible on T1WI. Diffuse cord enlargement is observed at the cervicothoracic junction.

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Fig. 7-41 Gadolinium-enhanced MR of intramedullary metastasis of colon cancer. Round, enhancing mass is identified after contrast infusion at the T3 level.

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Fig. 7-42 Gadolinium-enhanced axial MR of intramedullary metastasis of colon cancer. The intramedullary enhancing lesion is located at the right side in the spinal cord.

REFERENCES

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2 Townsend N, Handler M, Fleitz J, et al. Intramedullary spinal cord astrocytomas in children. Pediatr Blood Cancer. 2004;43:629-632.

3 Kim MS, Chung CK, Choe GY, et al. Intramedullary spinal cord astrocytoma in adults: Postoperative outcome. J Neurooncol. 2001;52:85-94.

4 Chang UK, Choe WJ, Chung SK, et al. Surgical outcome and prognostic factors of spinal intramedullary ependymomas in adults. J Neurooncol. 2002;57:133-139.

5 Hasselblatt M, Paulus W. Sensitivity and specificity of epithelial membrane antigen staining patterns in ependymomas. Acta Neuropathol. 2003;106:385-388.

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