Photo 35

Slide 35 depicts a mass lesion on the left side of the photograph. Note the substantial mass effect and the infiltrative character of the tumor. It is difficult to see its boundaries. Note the relatively homogeneous character of the mass due to an absence of hemorrhage and obvious necrosis. Hemorrhage and necrosis are gross features of higher grade tumors which produce a variegated appearance. What do you think this tumor is? The answer is astrocytoma. The next 3 gross photographs are all astrocyte lineage neoplasms (36, 37 and 38). Bring up each. Note the variegated appearance of the tumor in 36. This is a higher grade neoplasm. Both tumors in 37 and 38 are crossing the corpus callosum. This plus their highly varied gross morphology with areas of necrosis allow the diagnosis of Glioblastoma Multiforme ( grade IV astrocytoma). Tumors of the sort depicted in 35-38 tend to occur in adults.

Photo 36 & Photo 37 & Photo 38

Photo 39 & Photo 40

Now lets look at slide 39, a photograph of the base of the brain. Can you see the pathology? Look at the pons. Note how large it is. You might best perceive this by observing that the Basilar artery, normally seen on the pontine surface, is "buried" within the expanded pontine mass. You might also see that the cut surface of the brain stem is not quite right. This is an infiltrating pontine astrocytoma, a lesion usually seen in children. In picture 40 you will see the cut section of the lesion.

Photograph Pilo1 (below) is a cystic, cerebellar, pilocytic astrocytoma which killed the patient by causing cerebellar herniation with secondary brain stem hemorrhage and necrosis. Pilocytic astrocytomas are an important category of astrocytoma to recognize. Unlike low grade, diffuse, cerebral hemispheric fibrillary astrocytomas, such as the tumor in photo 35, they don’t tend to be highly infiltrative, nor do they tend to develop malignant transformation. If they are in a resectable location, outcome can be excellent. The cerebellum, optic nerve, chiasm, tracts and hypothalamus are all sites for this type of tumor. Pilocytic astrocytomas are usually tumors of children and young adults. The histology of pilocytic astrocytoma can be quite varied. Features such as microvascular proliferation, a negative finding in fibrillary astrocytoma, do not appear to be indicators of negative outcome. Photograph 40b is a typical microscopic field with Rosenthal fibers, a useful "marker" for this tumor. Here it is important to note, that Rosenthal fibers are not specific for this tumor, or even for a tumor diagnosis. They are frequent in certain benign cysts, such as simple pineal cysts.

Photo 41 & Photo Oligo

Slide 41 is an example of another class of primary brain tumor. What is you dx? Note the neoplasm is diffusely infiltrative and that it has small cyctic areas. When we cut this we noted gritty areas of calcification. The photomicrograph on slide Oligo shows the monotonous histology of this tumor, an oligodendrogliona.

Photo 43 & Photo 44

Slide 43 shows a hemorrhagic mass. Where is it? What is it likely to be? The location is 4^th ventricle and the mass is a ependymoma. The hemorrhage is partly, or completely the result of surgery. For typical histology look at slide 44 which shows a typical ependymoma type of perivascular pseudorosette. Note the finely fibrillated character of the cell processes surrounding the microvessel in the center of the field. These lesions tend to be in the first 2 decades of life.

Photo 45

Slide 45 is a pretty much a diagnostic image when seen in a child’s brain, as in this case. What is your diagnosis? Medulloblastoma, yes! In some classifications this tumor is listed with the PNETs (primitive neuroectodermal neoplasms This neoplasm has a great proclivity to seed the subarachnoid space. What types of cells make up this lesion?

Photo 46 & Photo 46a

Slide 46 shows cranial bone with a firmly attached mass. This meningioma was in the frontal region of an elderly woman. It was discovered as an "incidental" autopsy finding.

Photo 46a depicts a frontal lobe section with a similar large meningioma.

Photo 47

Slide 47 shows a meningioma invading the overlying bone. Meningiomas arrise from meningothelial ( arachnoid) cells. They are usually benign but, as you can see in 47, locally invasive. Bone invasion is not a sign of malignancy in the case of meningioma.

Photo 48 & Photo 49

Slide 48 shows a tumor at the cerebellar-pontine angle. It was attached to the 8^th cranial nerve. It is an---, acoustic schwannoma. What diagnosis would you make if the patient had 2 such lesions? Neurofibromatosis is the correct response.

Slide 49 shows a patient with neurofibromatosis with extensive paraspinal neurofibroma. How do you distinguish schwannoma from neurofibroma. How many genetic flavors of neurofibromatosis do you know? What other lesions do patients with this disorder manifest.

Slide 51:

Slide 51 displays a colloid cyst. These are always in this location and no where else. They may intermittently obstruct the ventricle. They can cause sudden death.

Slide 52

Slide 52 displays two separate pathological processes. The subtle one has the advantage of an arrow pointing at it. It is what? Perhaps you will answer this question better once you have had the section on demyelinating disease. Yes, it is a multiple sclerosis periventricular plaque. Now to the two black ball shaped lesions. Note their distribution, at the grey/white boundary. This distribution suggest a hematogenous (embolic) distribution. In this instance we are seeing metastatic melanoma.

Slide 54:

Slide 54 the last slide in the tumor section shows a frontal coronal section of a brain which exhibited dramatic diffuse white matter edema of the right hemisphere. This brain also had a very small focus of metastatic carcinoma. It illustrates the point that considerable edema may accompany a neoplasm. In this patient it resulted in hermispheric transtentorial herniation.