digest on pathomorhology

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Squamous elements most commonly are histologically benign in appearance (called adenocarcinoma with squamous metaplasia or more traditionally, adenoacantoma) when associated with well-differentiated adenocarcinomas.

Although classification as a poorly differentiated adenocarcinoma typically requires a less of glandular differentiation and the presence of solid growth, two histologic patterns behave as poorly differentiated regardless of their degree of differentiation and include papillary serous carcinoma.

Carcinoma of prostate gland

Cancer of the prostate is the second most common form of cancer in males, followed in frequency by lung cancer. It is a disease of men above the age of 50 years and its prevalence increases with increasing age so that 60% or more of men 80 years old have asymptomatic carcinoma of the prostate.

Precursor for prostatic cancer:

Androgens level is high.

Administration of estrogens.

In patients with Klinefelter’s syndrome.

Racial and geographic influences (in Americans).

Nodular hyperplasia.

There are following 4 types carcinoma of the prostate:

1.Latent carcinoma. This is found unexpectedly as a small focus of carcinoma in the prostate during autopsy studies in men dying of other causes. Its incidence in autopsies has been variously reported as 25-35%.

2.Incidental carcinoma. About 15-20% of prostatectomies done.

3.Occult carcinoma. This is the type in which the patient has no symptoms of prostatic carcinoma but shows evidence of metastases on clinical examination and investigations.

4.Clinical carcinoma. Clinical prostatic carcinoma is the type detected by rectal examination and other investigations and confirmed by pathologic examination of biopsy of the prostate.

Morphology

Macroscopically, the prostate may be enlarged, normal in size or smaller than normal. In 95% of cases, prostatic carcinoma is located in the peripheral zone, especially in the posterior lobe. The malignant prostate is firm and fibrous. Cut section is homogeneous and contains irregular yellowish areas.

Microscopically, there are 4 histologic types of cancer of the prostate adenocarcinoma,

transitional cell carcinoma, squamous cell carcinoma and undifferentiated carcinoma.

Metastases:

Lymphogenous: sacral, iliac and para-aortic lymph nodes.

Hematogenous: pelvis, lumbar spine, lungs, and kidneys, brain.

Liver tumors

Benign tumors

1.Liver cell adenomas are pale, yellow-tan, and frequently bile-stained nodules, found anywhere in the hepatic substance but often beneath the capsule.

They may reach 30 cm in diameter. Although they are usually well demarcated, encapsulation may not be macroscopically evident.

Microscopically, liver cell adenomas are composed of sheets and cords of cells that may resemble normal hepatocytes or have some variation in cell and nuclear size. Portal tracts are absent; instead prominent arterial vessels and draining veins are distributed through the substance of the tumor. A capsule that rahges from delicate collapsed reticulin to welldefined connective tissue usually separates the lesion from the surrounding parenchyma, but it may be deficient in places or entirely absent.

2.Bile duct adenomas are firm, pale, and usually single discrete nodules rarely more than I cm in diameter, frequently found in a subcapsular location, in contrast to the liver cell adenoma, they are almost never bile stained.

Microscopically they are composed of uniformly sized, epithelium-lined channels or ducts separated by a scant-to-abundant connective tissue stroma and sharply demarcated from

the surrounding liver.

Malignant tumors

1. Hepatocellular carcinoma may appear macroscopically as a unifocal (usually large) mass; multifocal, widely distributed nodules of variable size; or a diffusely infiltrative cancer, permeating

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widely and some times involving the entire liver.

All three patterns may cause liver enlargement (2000 to 3000 gm), particularly the unifocal massive and multinodular patterns.

The diffusely infiltrative tumor may blend imperceptibly into a cirrhotic liver background.

When discrete masses can be seen, they are basically yellow-white, punctuated sometimes by areas of hemorrhage or necrosis.

Hepatocellular carcinoma sometimes takes on a green hue when composed of welldifferentiated hepatocytes capable of secreting bile.

All patterns of hepatocellular carcinoma have a strong propensity for invasion vascular channels. Hepatocellular carcinoma range from well-differentiated to highly anaplastic undifferentiated lesions.

In well-differentiated and moderately well-differentiated tumors, cells recognizable as hepatocytic in origin are disposed either in a trabecular pattern or in an acinar, pseudoglandular pattern.

Supporting connective tissue is minimal to absent, explaining the soft consistency of most hepatocellular carcinoma. Bile may occasionally be seen in canalicular spaces or lumens between tumor cells, and bile canaliculi may be present ultrastructurally.

A distinctive variant of hepatocellular carcinoma is the fibrolamellar carcinoma. This tumor occurs in young men and women (20 to 40 years of age) with equal incidence, has no association with HBV or cirrhosis factors, and has a distinctly better prognosis. It usually constitutes a single large, hard “scirrhous” tumor with fibrous bands coursing through it.

Histologically it is composed of well-differentiated polygonal cells growing in nests or cords and separated by parallel lamellae of dense collar bundles, hence the name “fibrolamellar.”

2.Cholangiocarcinomas resemble adenocarcinomas arising in other parts of the body.

Cholangiocarcinomas are rarely bile stained because differentiated bile duct epithelium does not synthesize pigmented bile.

Most are well-differentiated sclerosing adenocarcinomas with clearly defined glandular and tubular structures lined by somewhat anaplastic cuboidal to low columnar epithelial cells. These neoplasms are often markedly desmoplastic; so dense collagenous stroma separates the glandular elements. Mucus is frequently present within cells and the lumina but not bile.

Tumors of the adrenal medulla

The two principal types of tumour of the adrenal medulla are pheochromocytomas (occurring in adults) and neuroblastomas (occurring in children).

Pheochromocytoma consists of secreting cells of the adrenal medull. It produces high levels of adrenaline/noradrenaline hormones and their breakdown products, vanyl mandelic acid (VMA) and homovanillic acid (HVA), both of which are excreted in the urine and can be estimated as a diagnostic test.

Macroscopically, the tumor is usually spherical and less than 5 cm in diameter, it has a pale, creamy cut surface that changes to dark brown almost instantly when exposed to air, due to oxygenation of tumor pigments. Despite the fact that the tumor is usually small and nonmetastatic, it is a hazardous condition with high perioperative mortality.

The excessive amine production produces hypertension that is often initially paroxysmal and associated with severe headaches, but the hypertension eventually becomes constant.

There may be intractable, and often unexplained, cardiac failure.

Pheochromocytoma is one of the causes of surgically treatable systemic hypertension.

Thyroid cancer

There are four main types of malignant tumor derived from thyroid follicle cell.

1.The most common type is papillary carcinoma, a well-differentiated tumor that arises most frequently in young adults. It is often multifocal within the thyroid, and tends to metastasize via lymphatics to nodes in the neck. It is slow-growing and has an excellent prognosis; even metastatic tumors grow slowly and can be cured by surgical resection.

2.Follicular carcinoma most commonly affects middle-aged people. Metastasizing via the bloodstream, it is one of the tumors that characteristically spread to bone. Patients may occasionally present with a spontaneous fracture due to metastatic disease, before the primary tumor is detected. It has a good prognosis.

3.Medullary carcinoma is a less frequent derived from parafolicular or C-cells and characterised by fibrovascular septa and amyloid-conteining stroma, irregular calcification, atypical cells.

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4.Entirely confined to the elderly, anaplastic carcinoma grows very rapidly, extensively invading tissues near the thyroid, such as the trachea and soft tissues of the neck. It may present with a rapidly enlarging thyroid mass causing tracheal compression or jugular vein invasion. The prognosis is very poor. The cells of the tumor, which are usually small, undifferentiated and round, must be distinguished histologically from malignant lymphoma; the latter can also affect the thyroid in the elderly, but is more responsive to treatment.

Pancreatic islet cell tumors

Islet cell tumors may be hormonally inactive or may produce hyperfunction.

These tumors make one or more of the following: glucagon, insulin, gastrin, somatostatin, vasoactive intestinal polypeptide (VIP), pancreatic polypeptide (PP).

The tumors are usually slow-growing, even when malignant (10% of total, higher for glucagonomas, gastrinomas, ACTH-omas and somatostatinomas).

The surrounding pancreatic islets may show hyperplasia,

Metastatic spread remains the only reliable criterion for malignancy in these tumors.

They are named according to their histogenesis:

Beta cell tumors ("insulinomas")

the most common islet cell tumors (* but their incidence is only about 1 in 1,000,000 people)

Look for Whipple's triad:

1.low measured plasma glucose (hypoglycemia);

2.mental changes, especially related to fasting or exercise;

3.attacks relieved by glucose administration.

Often, patients become massively obese.

The etiology of these tumors is obscure; there's not even an important genetic syndrome.

Of beta-cell tumor patients, 70% have a solitary adenoma, while the rest have either hyperplasia of many islands, or a beta cell carcinoma.

Grossly: usually solitary and well-encapsulated. Size from0/5 to 10cm.

Microscopically: cords and sheets of well-differentiated B-cells which do not differ from normal cells.

Many mesotheliomas and retroperitoneal fibrosarcomas, and occasionally other tumors, produce an insulin-like activity (probably somatomedin, but it varies).

Gastrinomas (Zollinger-Ellison Syndrome; "G-cell tumors")

An especially troublesome syndrome of multiple bleeding ulcers and diarrhea. The majority of gastrinomas are low-grade malignancies. May be benign and malignant.

Gastrinomas occur in the wall of the duodenum.

High basal acid secretion plus a marked increased in serum gastrin levels in response to secretin administration strongly suggests gastrinoma.

Glucagonomas ("alpha-two cell tumors"). These produce mild diabetes, sore tongue, and necrolytic migratory erythema. Don't miss this diagnosis.

Delta cell tumors ("somatostatinomas"): diabetes, diarrhea, gallstones, etc.

Tumors secreting vasoactive intestinal polypeptide ("VIPomas"; "VernerMorrison syndrome"): pancreatic cholera (horrible diarrhea), loss of potassium, achlorhydria -- excellent response to somatostatins.

PP-omas ("P-cell tumors"): no syndrome despite huge amounts of pancreatic polypeptide

Multiple Endocrine Neoplasia Syndromes ("MEN", formerly "MEA", adenomas): some or all of the following in same family:

Wermer's MEN I: pituitary adenoma, parathyroid adenoma, Zollinger-Ellison

Sipple's MEN II(a): Parathyroid adenoma, pheochromocytoma, medullary carcinoma of the thyroid

MEN IIb/III: Medullary carcinoma of the thyroid, pheochromocytoma, mucosal neuromas, Marfanoid habitus.

MESENCHYMAL TUMORS

In ontogenesis, mesenchyma gives the beginning to

1)connective tissue,

2)vessels,

3)muscles,

4)tissues of musculoskeletal system,

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5)serous membranes,

6)hemopoietic system. Mesenchymal tumors develop from

1)connective (fibrous) tissue,

2)fat tissue,

3)muscular tissue,

4)blood and lymphatic vessels,

5)synovial tissue,

6)mesothelial tissue,

7)bone tissue.

They may be benign (name of the tissue + oma) and malignant (name of the tissue + sarcoma). There are also special terms (e.g. desmoid, granular-cell tumor).

Connective (fibrous) tissue tumors

Main benign connective (fibrous) tissue tumors

1)Fibroma - a node of differentiated connective tissue with different direction of the bands:

Dense -fibrous structures prevail over the cellular elements.

Soft (loose connective tissue with great amount of stroma cells -fibroblasts and fibrocytes).

Localization of fibroma is various: skin, breast.

2)Desmoid fibroma is a kind of dense fibroma and characterized by infiltrating growth and relapses.

It is composed of banal, “tame-looking” fibroblasts that do not metastasize. More often it is located on the anterior abdominal wall.

3)Dermatofibroma (histiocytoma) - small fibrous node with yellow-brown color. More often it is located in the skin of the legs. Histologically, dermatofibromas are composed of intertwined and anastomosing bundles of fibroblasts surrounded by dense collagen. There are giant polynuclear cells with lipids and hemosiderin between cells.

Malignant connective (fibrous) tissue tumors

Macroscopically sarcoma looks like “fish flesh”. As a rule sarcoma metastases are disseminated hematogenically. Tumors are characterized by atypical cells, including loss of the structure.

1)Fibrosarcoma occurs in deep soft tissue sites, showing increased fibroblastic cells, anaplasia, and abundant mitotic figures. It looks like node or encapsulated formation. There are 3 types of fibrosarcoma:

Differentiated fibrosarcoma is characterized by prevalence of fibrous component over cellular component.

Poorly differentiated fibrosarcoma, termed cellular sarcoma. It is characterized by prevalence of cellular component over fibrous component. It produces metastases more frequently.

Round-cell tumors of unknown origin, termed unclassified tumor.

2)Dermatofibrosarcoma protruberans (malignant histiocytoma)

It is essentially a well-differentiated, slow-growing fibrosarcoma of the skin. It is locally aggressive but rarely metastasizes.

Grossly, they are multilobulated gray-white, fleshy, infiltrative, and unencapsulated but deceptively circumscribed.

Microscopically, there are cellular neoplasm composed of radially oriented (“storiform”) fibroblasts, showing spindled and polygonal cells; mitoses are not as numerous as in fibrosarcoma.

The overlying epidermis is thinned and there often is microscopic extension into subcutaneous fat.

Tumors of fatty tissue

Benign:

1.Lipoma

It is the most frequent soft tissue tumors, arising in subcutaneous regions at any site but most commonly on the back, shoulder, and neck.

They can also arise in the mediastinum, retroperitoneum, or bowel wall.

It may develop in every site where there is fat tissue.

Lipomas are encapsulated, usually small yellow node.

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Intramuscular infiltrating lipoma is a tumor without distinct (clear) borders, it infiltrates to intermuscular connective tissue.

2.Hybernoma is a rare tumor of brown fat and consists of large round cells with granular or foamy cytoplasm (fat vacuoles).

Malignant:

1.Liposarcoma (lipoblastic myoma) is a rare, large tumor, which is composing of lipocytes of different degree of maturity and lipoblasts. There are several types of liposarcoma:

a)Well differentiated (lipoma-like) liposarcoma.

b)Myxoid (embryonic) liposarcoma tend to be low-grade tumors, which are stubbornly recurrent, follow a more protracted course, and metastasize late.

c)Round-cell liposarcoma.

d)Pleomorphic liposarcoma are high-grade, aggressive sarcomas (85-90% metastasize).

2.Malignant hybernoma is a very rare tumor with cellular polymorphism and a lot of giant cells.

Tumors of the muscles

Benign:

1.Leiomyoma

Leiomyoma consists of smooth muscle with chaotic (confused) location of the muscular tissue bands, the stroma with vessels and nerves.

If stroma prevails this tumor is termed fibromyoma.

Leiomyomas occur predominantly in the female genital tract, but they may also occur at other body sites where smooth muscle is well represented (scrotum, nipple, bowel wall).

Secondary changes: necrosis, hemorrhages, cysts, hyalinosis, petrifaction are characterized for leiomyomas.

2.Rhabdomyoma

Rhabdomyoma consists of striated muscles. It resembles embryonic muscular fibers and myoblasts.

It appears against a background of tissue shifts and is accompanied by other development defects (large masses of striated muscles).

The tumors are most frequently primary tumor of the heart in infants and children and are frequently discovered in the first years of life because it leads to obstruction of valve orifice or cardiac chamber.

3.Granular-cell tumor (Abrikosov's tumor): this is small tumor in a capsule. It is located in the tongue, esophagus, and skin. The cells have round shape, large with granular cytoplasm (no lipids).

Malignant:

1.Leiomyosarcoma (malignant leiomyoma) with cellular and tissue atypism, a large number of mitoses (high mitotic index) are characteristic. These rare tumors arise in the skin, deep soft tissues, the stomach and particularly in the uterus from pre-existing myomas.

2.Rhabdomyosarcoma (malignant rhabdomyoma) is a more common, especially in children, in the head and neck and urogenital region. It is subdivided into four types based on the morphologic features:

The pleomorphic type occurs in patients over 45 years. This variant has large, atypical tumor cells, some showing abundant cytoplasm with cross striations characteristic of skeletal muscle differentiation.

Embryonal, botryoid, alveolar types are poorly differentiated tumors of small blue cells that have focal skeletal muscle differentiation (rhabdomyoblasts with abundant eosinophilic cytoplasm or cross striations). The botryoid pattern is basically a morphologic variant of embryonal, with grape-like masses projecting into a cavity such as: vagina, bladder. These tumors may be apparent only with immunohistochemical investigation.

3.Malignant granular-cell tumor (malignant myoblastoma) resembles malignant rhabdomyoma but the cytoplasm is granular.

Tumors of synovial tissue

1.Benign synovioma develops in the tendons and tendon sheath. It contains a lot of stroma with hyalinosis, and a little number of vessels. There may occur xanthomic cells and clefts.

2.Synovial sarcoma (malignant synovioma) develops around the large joints (but not in joint spaces), in the parapharyngeal region, in the abdominal wall, and less commonly at other body sites. It has

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polymorphic structure. Some tumors have polymorphic cells and pseudoepithelial gland formations with cysts, the other have fibroblastoid atypical cells and collagen fibers, structures resembling tendons.

Tumors of mesothelial tissue

1.Benign mesothelioma resembles a dense node in serous membrane (pleura); its structure is similar to fibroma (fibroid mesothelioma).

2.Malignant mesothelioma (peritoneum, pleura, pericardium) microscopically looks like atypical large cells with vacuolized cytoplasm. Malignant mesothelioma may has tubular and papillary structures. Mesothelioma with tubular and papillary structures is called epithelial mesothelioma.

Tumors from blood and lymph vessels

Benign tumors from blood vessels and lymph vessels

1.Hemangioma is a tumor from blood vessels. There are several types of hemangioma:

a)Capillary, which develops in the skin, mucous membranes, gastrointestinal tract, liver, more often in children. Capillary hemangiomas are well-defined but unencapsulated lobules. These lobules are composed of capillary-sized, thin-walled, blood-filled vessels. These vessels are lined by single layer of plump endothelial cells surrouded by a layer of pericytes.

b)Cavernous hemangioma locates in the liver, skin, bones, muscles, gastrointestinal tract, brain. They are single or multiple, discrete of diffuse, red to blue, soft and spongy masses. They are often 1 to 2 cm in diameter. Cavernous hemangiomas are composed of thin-walled cavernous vascular spaces, filled partly or completely with blood.

2.Glomus tumor (glomus angioma). Glomus tumor is an uncommon true benign tumor arising from contractile glomus cells that are present in the arteriovenous shunts. These tumors are found most often in dermis of the fingers or toes under a nail. These lesions are characterized by extreme pain. Microscopically: the tumors are composed of small blood vessels lined by endothelium and surrounded by aggregates of glomus cells. The glomus cells are round to cuboidal cells with scanty cytoplasm. The intervening connective tissue stroma contains some non-myelinated nerve fibres.

3.Lymphangiomas growth of lymphatic vessels in different direction with formation of a node or enlargement of the organ. If lymphangioma develops in the tongue, it is termed macroglossia; if lymphangioma develops in the lip it is termed macrocheilia.

a)Capillary lymphangioma is small, circumscribed, slightly elevated lesion measuring 1 to 2 cm in diameter. It is composed of a network of endothelium-lined, capillary-sized spaces containing lymph and often separated by lymphoid aggregates.

b)Cavernous lymphangioma is more common than capillary type. It consists of large dilated lymphatic spaces lined by flattened endothelial cells and containing lymph. A large cystic variety called cystic hydroma occurs in the neck producing gross deformity.

Malignant tumors from blood vessels and lymph vessels

1.Angiosarcoma also known as hemangiosarcoma and malignant hemangioendothelioma, it is a malignant vascular tumor occurring in the skin, subcutaneous tissue, liver, spleen, lung and retroperitoneal tissues. The tumor is usually well-defined, gray-red, polypoid mass. The tumors may be well-differentiated masses of proliferating endothelial cells around well-formed vascular channels, to poorly-differentiated lesions composed of plump, anaplastic and pleomorphic cells in solid clusters with poorly identifiable vascular channels.

2.Malignant hemangiopericytoma is a tumor arising from pericytes. Pericytes are cells present external to the endothelial cells of capillaries and venules. The tumor is composed of capillaries surrounded by spindle-shaped pericytes outside the capillary basement mambrane forming whorled arrangement. Silver impregnation stains are employed to confirm the presence of pericytes outside the basement mambrane of capillaries and to distinguish it from hemangioendothelioma. These tumors are highly malignant with early metastases in skin, liver, and muscles.

3.Kaposi’s sarcoma is a malignant angiomatous tumor, first described by Kaposi, Hungarioan dermatologist, in 1872. However, the tumor has attracted greater attention more recently due to its frequent occurrence in patients with AIDS. Presently, four forms of Kaposi‟s sarcoma are described:

Classic (european) Kaposi’s sarcoma. Thedisease is slow and appears as multiple, small, purple, dome-shaped nodules or plaques in the skin, especially on the legs.

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Chondrosarcomas are malignant tumor consisting of cartilage.

It may be primary and secondary. Primary chondrosarcoma originates in bones the trunk (pelvis, vertebrae, ribs) and adjacent proximal ends of long bones of the extremities.

Secondary chondrosarcoma develops from preexisting chondromas.

Depending on their location, there are peripheral and central chondrosarcomas.

The tumor tissues have a graish-white, glassy consistency.

There are also characteristic, irregular, partly mucinous, partly hemorrhagic areas of necrosis as well as pseudocysts.

The cortex is breached in several areas, and the spongiosa is invaded.

Microscopically: atypical cartilage with plump nuclei; frequent multinucleated cells, pleomorphism, two or more cells in the lacunae.

TUMORS OF NERVOUS SYSTEM AND BRAIN MEMBRANES

Tumors of nervous system develop from different elements of the nervous system:

1.Central.

2.Vegetative.

3.Peripheral.

4.Mesenchymal elements, which are also a part of this system.

Astrocyte tumors or gliomas

The most frequent brain tumors.

They develop from astrocytes and can be found in all brain portions.

The highest incidence is observed between the ages 25 - 45.

The diameter of the tumor is about 5-10 cm. They do not always have distinct boundaries with the surrounding tissue. It is homogeneous on incision. As a rule, considerable enlargement of the brain portions is observed.

Astrocytoma is characterized by cyst formation (one or several). They contain colloid substance or yellowish fluid with large amount of protein.

There are three histological types of astrocytoma:

1.Fibrillar tumor is rich in glial fibers looking like parallel bands, it contains small amount of astrocytes.

2.Protoplasmatic astrocytoma consists of different in size cells with processes, which resemble astrocytes; their processes form thick interlacing.

3.Fibrillar-protoplasmatic tumor is characterized by even location of astrocytes and glial cells.

Cerebellar astrocytoma and subependymal astrocytoma are separate subtypes. A malignant type is astroblastoma characterized by rapid growth, polymorphism and necroses in the tumor. This tumor is rare, it disseminates through the liquor routs.

Oligodendroglial tumors

In the majority of cases these are benign.

The highest incidence is observed at the age of 30 - 40. In rare cases, they occur in children.

They are mainly localized in the large hemispheres of the brain, more seldom in the region of visual tuber and in the trunk. Very seldom, they develop in the area of cerebellum and spinal cord. Primary multiple oligodendrogliomas of meninges and visual nerves were also described.

Macroscopically, the tumor is pinkish-gray, resembles brain substance and is diagnosed by the enlargement of the brain portion. Its consistency may be paste-like; when calcifications are present it may be dense.

Microscopically it consists of homogeneous small cells with round nuclei and narrow outline of cytoplasm, which is poorly colored. Sometimes it is characterized by the structure resembling honeycombs. The tumor is usually poor in vessels. Hyalinosis and calcification may also be observed.

The types of oligodendrogliomas are fusiform cell and polymorphocellular.

A malignant type of the tumor is oligodendroglioblastoma characterized by special cell location, marked polymorphism with giant cells. It is also characterized by numerous mitoses and necrosis foci. The metastases spread through the liquor routs, more often along the walls of the ventricles. Symmetrical location of the tumor nodes in the walls of the ventricles is typical.

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Ependymal tumors and tumors of choroid epithelium

Three types of ependymal tumors are distinguished.

1)Ependymoma (glioma connected with ventricular ependymoma) looks like intraor extraventricular node.

The foci of necrosis and cysts can be found in it

Clasters of uniand bipolar cells around the vessels (so-called pseudorosettes) and cavities covered with epithelium (true rosettes) are typical.

Most frequently they are located in caudal portions of rhomboid fossa. Ependymoma may go down the spinal canal (craniospinal tumors).

Ependymoma is usually localized in the bed of the 4th ventricle and in the 3th ventricle.

In the area of the spinal cord, they first grow intramedullary, and then become extramedullar.

Macroscopically they look like nodes of different size with tuberous (4th ventricle) or villous (lateral ventricle) surface. The color is pinkish-gray; the consistency is soft.

Microscopic study reveals perivascular structures of radially located cells. Their processes form a fibrous ring between the body of the cell and the wall of the vessel and over the body of the cell. In the rest of the tumor tissue, the cells are located in mosaic manner. Single and multiple clefts and tubes bedded with cylindrical epithelium are common.

2)Ependymoblastoma is a malignant type of ependymoma. This is characterized by marked cellular polymorphism. It grows quickly, metastases spread through the liquor system. Dedifferentiated ependymoma is a transitory form between the two types: Choroid papilloma, Choroid carcinoma.

1.Choroid papilloma is a tumor from the epithelium of vascular plexus, looking like a villous node in the cavity of the brain ventricle.

It is mainly observed in young people.

It consists of numerous, villous structures of cubic or prismatic epithelial cells. It is located within the brain ventricles. Heterotopic types are rare (horse‟s tail).

Macroscopic study demonstrates well-outlined nodes of various sizes. The surface of the tumor is smallor large-villous, has caulifloweror mulberry-like appearance. Consistency is either dense or soft; the color is pinkish-gray.

Microscopically it consists of villi; their connective-tissue stroma is covered with cubic or cylindrical epithelium. Hyalinosis can be frequently observed.

2.Choroid carcinoma is a malignant type of choroidpapilloma. It is made of anaplastic cells covering the vascular plexus. Papillary cancer is a rare tumor.

3)Neuronal tumors:

Ganglioneuroma is a rare mature tumor. Most frequently it is localized in the bed of the 3th ventricle, seldom in the hemispheres of the brain. It usually occurs in children and juveniles. The tumor consists of mature ganglionic cells divided with the bands of glial stroma. Macroscopically ganglioneuroma looks like a limited node. In the medulla oblongata it is diffuse, in the cerebellum it looks like hyperplastic folds.

Cerebellum ganglioma is characterized by proliferation of large nervous elements of Purkinier's cell type.

Ganglioneuroblastoma is a malignant analogue of ganglioneuroma (malignant gangliocytoma). This is an extremely rare tumor of CNS. It is characterized by cellular polymorphism and similar to malignant glioma.

Neuroblastoma is a rare highly malignant brain tumor. It occurs mainly in children. The tumor is formed from large cells with bubble-like nucleus. Mitoses are numerous. The cells grow like sincitium. There are a lot of vessels.

Poorly differentiated and embryonic tumors

Medulloblastoma and glioblastoma belong to this group. The latter occurs in children.

1.Medulloblastoma is a tumor made by immature cells, medulloblasts; therefore it is highly malignant.

The most frequent idealization is vermis cerebelli.

Macrpscopically, it is pinkish-gray.

Microscopically medulloblastoma consists of homogenous small cells with dark round or oval nucleus and poorly seen rim of cytoplasm. The cells are located close to each other. Rosette is typical. Mitoses are numerous. Vessels are not numerous.

Metastases spread through the liquor routs.

2.Glioblastoma is the second (after astrocytoma) in the incidence. Synonyms: multiform glioblastoma, glioblastoma, spongioblastoma.

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It occurs at the age of 40 - 60.

It is situated in the white substance of the brain. This tumor is mainly located in the large hemispheres of the brain, sometimes in the trunk.

It is characterized by rapid infiltrative growth without distinct boundaries.

Glioblastoma usually produces regional metastases; those to the inner organs are rare (lungs).

Macroscopically it is motley-colored due to necroses and hemorrhages.

Microscopically the tumor is characterized by marked polymorphism. The cells are located disorderly (cellular chaos), their size and shape are various, from small lymphocyte-like to giant polynuclear. Necroses, hemorrhages and vascular growths are typical. Mitoses and centers of atypical division are frequent.

Meningovascular tumors

These tumors appear from the meninges. The most frequent is meningioma and its malignant variant meningeal sarcoma.

1.Arachnoidendothelioma (meningioma)

Arachnoidendothelioma (meningioma) is the most frequent type of meningovascular tumors. They mainly occur in adults over 30, while in children, they are rare. It is also termed psammoma.

They are characterized by slow expansive growth.

Arachnoendothelioma is usually localized in I) longitudinal sinus and Paccionian bodies, 2) convex, 3) falciform process, 4) olfactory region, 5) wings and body of main bone, 6) tubercle of the saddle, 7) the region of semilunar node of trigeminal nerve, 8) tentorium cerebelli, 9) vascular plexi.

Macroscopically, arachnoidendothelioma looks like well-limited solitary (in rare cases, multiple) nodes; their consistency is dense, elastic. The tumor is on incision they are grayish-pink with light bands.

Microscopically large endothelium-like cells characterize it. The cells usually form groups (plate-like, curl-like, band-like), so-called endotheliomatous structures. In these tumors, there are secondary changes (calcifications, psammoma bodies, paste).

Types of arachnoidendotheliomas:

1.Endotheliomatous.

2.Fibrous arachnoidendothelioma with plenty of connective tissue fibers.

3.Meningotheliomatous characterized by microcircular structures.

4.Alveolar.

5.Xantomatous.

2.Meningeal sarcoma is malignant type of the tumor.

Histologically it resembles fibrosarcoma, polymorphocellular sarcoma, and diffuse sarcomatosis of the meninges.

Thus, morphogenetic variety of CNS tumors, difficult diagnosis and differential diagnosis as well as their localization allow including them into a separate group.

Special attention should be paid to development of secondary signs, which appear due to the influence on the craniobasal and distal regions of the brain.

Secondary syndromes are dislocation syndromes which are dangerous for the life of the patient; entrance of the temporal lobe to the tentorial foramen with strangulation of the midbrain; vasomotor vascular crises, heart failure; wedging of cerebellum tonsil to the great foramen; regional foci of circulation disturbance (insults and hemorrhages); epileptiform attacks.

Only correct diagnosis helps to determine the tactics of treatment for such patients.

Tumors of vegetative nervous system

Tumors of vegetative nervous system originate from ganglionic cells of different degree of maturity (sympathogonias, sympathoblasts, ganglioneurocytes) in sympathetic ganglia as well as from the cells of nonchromophinic paraganglia (glomes) genetically connected with sympathetic nervous system.

Such benign tumors as ganglioneuroma, paraganglioma (glomes tumor, chemodektoma) belong to this group.

Ganglioneuromas are localized in the medullar substance of the adrenal gland, sympathetic trunks, cerebrospinal nerves. It usually develops in young patients. The tumor