Carcinomas

Carcinoma of the lung is the most common primary malignancy to metastasize to the brain, followed by carcinomas of the breast, kidney, gastrointestinal

figure 1 1.45

Metastatic cerebral tumors. A. Tumor embolus in a leptomeningeal capillary from pulmonary carcinoma. B. Solitary metastatic carcinoma from the lung. The tumor presented approximately one and a half years after resection of a left lower lobe adeno-carcinoma in a 66-year-old man. Contrast-enhanced CT scan shows a circumscribed, round, hyperdense mass in the right frontocentral region at the junction of the cortex and white matter, surrounded by massive edema. C. On contrast-enhanced CT scan, a solitary carcinoma metastasis in the right central region from the lung appears as a ring-enhancing lesion. D. Horizontal section of the brain shows a necrotic and hemorrhagic tumor surrounded by edema. E. Multiple, widely dispersed bron-chogenic carcinomas. Contrast-enhanced T-1 weighted MRI of a 55-year-old man showing small ring-enhancing lesions in cerebral and cerebellar hemispheres and pons. F. Macrosection of the pons demonstrates several small, circumscribed metastatic tumors (LFB-CV). G. Multiple tiny metastases from skin melanoma resected 9 years prior to patient's death. H. Dural and bony metastases from prostate carcinoma in a 77-year-old man. The tumor was diagnosed 2 years prior to patient's death and was treated with radiation and chemotherapy. I. Dural spread of acute myelocytic leukemia in a 52-year-old man.

figure 1 1.45

Metastatic cerebral tumors. A. Tumor embolus in a leptomeningeal capillary from pulmonary carcinoma. B. Solitary metastatic carcinoma from the lung. The tumor presented approximately one and a half years after resection of a left lower lobe adeno-carcinoma in a 66-year-old man. Contrast-enhanced CT scan shows a circumscribed, round, hyperdense mass in the right frontocentral region at the junction of the cortex and white matter, surrounded by massive edema. C. On contrast-enhanced CT scan, a solitary carcinoma metastasis in the right central region from the lung appears as a ring-enhancing lesion. D. Horizontal section of the brain shows a necrotic and hemorrhagic tumor surrounded by edema. E. Multiple, widely dispersed bron-chogenic carcinomas. Contrast-enhanced T-1 weighted MRI of a 55-year-old man showing small ring-enhancing lesions in cerebral and cerebellar hemispheres and pons. F. Macrosection of the pons demonstrates several small, circumscribed metastatic tumors (LFB-CV). G. Multiple tiny metastases from skin melanoma resected 9 years prior to patient's death. H. Dural and bony metastases from prostate carcinoma in a 77-year-old man. The tumor was diagnosed 2 years prior to patient's death and was treated with radiation and chemotherapy. I. Dural spread of acute myelocytic leukemia in a 52-year-old man.

tract, prostate, and thyroid gland. Skin melanoma and choriocarcinoma are less common malignancies, but they have a high tendency to spread to the brain.

Metastases can present before or simultaneously with the primary malignancy and, importantly, they can also appear months or years after the surgical resection of their source. Being fast-growing tumors, edema and raised ICP develop early in the clinical course. Highly vascular tumors—such as melanoma, choriocarcinoma, and renal carcinoma—are prone to bleed, mimicking a stroke. The prognosis is generally poor. There are few exceptional case reports of long survival following resection of primary and metastatic tumors.

The location, number, and size of metastases vary greatly. They may occur at any site in the cerebrum, preferentially at the junction of the cortex and white matter (see Fig. 11.45). The choroid plexus, the pineal, and the pituitary glands are less common sites. Prostate carcinoma spreads commonly to the skull and dura (see Fig. 11.45). Metastases can be solitary, but they are more often multiple, varying from as many as 10 to 15 or more. Their sizes range from microscopic clusters of malignant cells to large masses.

Grossly, the tumors are fairly well circumscribed but poorly demarcated, contain hemorrhages and necrosis, and are surrounded by extensive edema. Histologi-cally, the picture varies from well-differentiated tumors resembling the primary tumor to anaplastic tumors. These may pose diagnostic difficulties, particularly when the primary malignancy is clinically not evident. Immunohistochemical studies for epithelial markers (cytokeratin, epithelial membrane antigen) support the carcinomatous origin of the metastasis.

Meningeal carcinomatosis or carcinomatous meningitis usually results from the spread of an intraparen-chymal carcinoma to the leptomeninges. The meninges are seldom the primary sites of metastases. Contrast-enhanced MRI and cytologic study of the CSF confirm the diagnosis.

Hematopoietic Metastases Lymphomas

The nervous system is involved in about 10% of non-Hodgkin's lymphomas and only rarely in Hodgkin's disease. Lymphomas can disseminate to the leptomenin-ges, diffusely or focally filling the subarachnoid space and infiltrating the cranial and spinal nerve roots. They can form nodules in the dura that compresses the adjacent tissue, and can also produce intracerebral mass lesions.

Leukemic Meningitis

Invasion of the leptomeninges in acute and chronic leu-kemias is high, averaging from 10% to 40%. It is noteworthy that prophylactic CNS therapy has led, in some instances, to the development of CNS tumors, particularly in young children.

Leukostasis

Occlusions of small parenchymal blood vessels by leukocytes occur in acute leukemias and in the blast crisis of chronic leukemias. Hemorrhages and infarcts are serious complications. Subdural and subarachnoid hemorrhages complicate thrombocytopenia.

TUMORS OF THE SPINAL CORD, NERVE ROOTS, AND MENINGES

Tumors within the spinal dural sac may arise in the spinal cord, nerve roots, and meninges. Their gross and histologic features generally resemble those of their intracranial counterparts.

Intramedullary Tumors

Gliomas with ependymomas and astrocytomas, are most frequently encountered within the spinal cord.

Ependymoma constitutes more than half of intra-medullary tumors. It is common in adults and may occur in any segment of the cord. The well-demarcated solid tumor is situated around the central canal (Fig. 11.46).

Myxopapillary ependymoma arises within the conus or filum terminale and is situated between the nerve roots of the cauda equina. Histologically, the tumor is composed of cuboidal and columnar ependy-mal cells arranged around blood vessels or aligned along the fibrous stroma in a papillary fashion. Mucoid degeneration is prominent (see Fig. 11.46).

Astrocytoma diffusely enlarges the cords of children and adults, usually in the cervical and thoracic

figure 1 1.46

Spinal cord tumors A. Intramedullary ependymoma (myelin stain). B and C. Histology of mixopapillary ependymoma (HE). D. Intramedullary angiomatosis (Perdrau stain). E. Schwannomas of the nerve roots (myelin stain). F. Carcinoma metastasis (cresyl violet).

figure 1 1.46

Spinal cord tumors A. Intramedullary ependymoma (myelin stain). B and C. Histology of mixopapillary ependymoma (HE). D. Intramedullary angiomatosis (Perdrau stain). E. Schwannomas of the nerve roots (myelin stain). F. Carcinoma metastasis (cresyl violet).

regions. The histologic features vary from benign to malignant. The tumor may be associated with syringomyelia.

Oligodendroglioma occurs rarely in the spinal cord and affects adults. Unlike its cerebral counterpart, calcification is uncommon.

Neuronal tumors, such as gangliocytoma and gan-glioglioma, are rare.

Capillary hemangioblastoma has the histologic features of its cerebellar counterpart and occurs in von Hippel-Lindau syndrome.

Angiomatosis may produce massive hemorrhages or a slowly progressive necrotizing myelopathy. Angiomatosis of the leptomeninges may also be present (see Fig. 11.46).

Spinal enterogenous cyst, a rare intra- or extramed-ullary lesion. may present from childhood to old age. The cyst wall is lined with columnar epithelial cells resembling intestinal epithelium.

Metastatic tumors are rare, but meningeal malignancies may extend into the cord along the perivascular spaces (see Fig. 11.46).

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