((General pathology))



((General pathology))

Vascular pathology in hypertension:

Hypertension not only accelerate atherogenesis but also cause degenerative changes in the walls of large and medium arteries that can lead to both aortic dissection and cerebrovascular hemorrhage.

Hypertension is also associated with two forms of small blood vessel disease and these are ( hyaline arteriolosclerosis and hyperplastic arteriolosclerosis).

Hyaline arteriolosclerosis

Vascular lesion consist of a homogenous pink hyaline thickening of the walls of arterioles with loss of underlining structural detail, and with narrowing of the lumen.

It seen frequently in elderly patients whether normotensive or hypertensive, but it is more sever and more generalized in patients with hypertension. It is also common in Diabetic patients.

Pathogenesis:

Leakage of plasma components across vascular endothelium and excessive extracellular matrix formation by smooth muscle cells secondary to hemodynamic stress of hypertension or to metabolic stress of diabetes that lead to endothelial cell injury.

Hyaline arteriolosclerosis usually involve kidney and lead to impaired renal blood supply, loss of nephrons, and symmetrical contraction of the kidneys.

Hyperplastic arteriolosclerosis:

it related to acute and more sever elevation in blood pressure, it characteristic to malignant hypertension (diastolic pressure usually over 120 mm Hg.).

microscopical appearance: onionskin laminated thickening of the wall of arteriole with progressive narrowing of the lumen, this laminations due to smooth muscle cells and thickened and reduplicated basement membrane. In sever cases the hyperplastic arteriolosclerosis associated with deposition of fibrinoid and acute necrosis of vessel wall referred to as ( fibrinoid necrotizing arteriolitis), particularly seen in the kidney.

Aneurysms:

localized , permanent , abnormal dilation of a blood vessel.

Types :

1- Atherosclerotic usually occur in abdominal aorta rupture of which can cause retroperitoneal hemorrhage.

2- Dissecting usually occur in thoracic aorta dissecting along the media causes vascular occlusion and haemopericardium.

3-Berry aneurysm: occur within the brain rupture of which cause subarachnoid hemorrhage.

4-Capillary microaneurysm: may be intracerebral (like in hypertension), or in the retina of the eye causing diabetic retinopathy.

5-Syphilitic : associate with syphilis and affect the thoracic aorta.

6-Mycotic: result of weakening of arterial wall secondary to fungal or bacterial infection, main site is the cerebral arteries, seen in accoiation with bacterial endocardities .

Giant cell (temporal) arteritis

Giant cell ( temporal) arteritis, the most common form of systemic vasculitis in adults, is an acute and chronic, often granulomatous, inflammation of medium-sized and small arteries. It affects

the arteries in the head-- especially the temporal arteries-- but also the vertebral and ophthalmic arteries. The latter may lead to blindness.

MORPHOLOGY.

Characteristically, short segments of one or more affected arteries develop nodular thickenings with reduction of the lumen, which may become thrombosed.

Histologically, two patterns are seen. In the more common variant, there is granulomatous inflammation of the inner half of the media centered on the internal elastic membrane marked by a mononuclear infiltrate, multinucleate giant cells of both foreign body and Langerhans type, and fragmentation of the internal elastic lamina .

Giant cells are present in only two thirds of cases of temporal arteritis, and many histologic sections may have to be examined before one is detected.

Pathogenesis.

The cause of this relatively common disease remains unknown. The morphologic alterations suggest an immunologic reaction against a component of the arterial wall, such as elastin. T cell-mediated injury is suspected..

Clinical Features.

The disease is most common in older individuals and rare before the age of 50. Clinically, it begins with only vague constitutional symptoms--fever, fatigue, weight loss--without localizing signs or symptoms, but in most instances there is facial pain or headache, which is severe, sometimes unilateral, and often most intense along the course of the superficial temporal artery. The vessel itself may be nodular and painful to palpation. More serious are ocular symptoms, which appear quite abruptly in about half of patients and range from diplopia to transient or permanent complete vision loss. Because treatment with anti-inflammatory agents is remarkably effective, there is urgency in establishing the diagnosis . The diagnosis depends on biopsy and histologic confirmation, but because of the segmental nature of the involvement, adequate biopsy requires at least a 2- to 3-cm length of artery, and a negative biopsy result does not rule

Buerger’s disease(thrombo-angiitis- obliterans):

It is a disease that often lead to vascular insufficiency, that affect medium sized and small arteries, mainly the tibial and radial arteries.

Previously the disease occurred almost exclusively among heavy cigarette smoking men, but the disease recently have be increasingly reported in women, due to smoking increases among women before age of 35 years.

Morphology:

The disease seen mostly in the upper and lower extremities, microscopical findings are:

1-Heavy mixed inflammatory cells infiltrate the arterial wall.

2-thromosis of the lumen, the thrombus contains small microabcesses.

Complications: chronic ulcerations and gangrene to the toes and fingers.

BENIGN TUMORS :

Hemangioma

As neoplasms characterized by an increased number of normal or abnormal vessels, they are most commonly localized; however, some involve large segments of the body, such as an entire extremity. The majority are superficial lesions, often of the head or neck, but they may occur internally, with nearly one third in the liver.

Hemangiomas are extremely common, particularly in infancy and childhood. Most benign pediatric angiomas--capillary and cavernous--are present from birth and expand along with the growth of the child. Nevertheless, many of the capillary lesions regress spontaneously at or before puberty.

Types of Hemangiomas:

Capillary Hemangioma.

Capillary hemangiomas, are composed of blood vessels that resemble capillaries, narrow, thin-walled, and lined by thin endothelium. Usually occurring in the skin, subcutaneous tissues, and mucous membranes of the oral cavities and lips, they may also occur in internal viscera, such as the liver, spleen. The strawberry type of capillary hemangioma (juvenile hemangiomas) of the skin of newborns is extremely common (1 in 200 births) and may be multiple. They grow rapidly in the first few months, begin to fade when the child is 1 to 3 years old, and regress by age 7 in 75 to 90% of cases.

MORPHOLOGY.

Varying in size from a few millimeters up to several centimeters in diameter, lesions are bright red to blue, level with the surface of the skin or slightly elevated, and usually have an intact covering epithelium. Occasionally, pedunculated lesions are formed, attached by a broad-to-slender stalk.

Histologically,capillary hemangiomas are usually lobulated but unencapsulated aggregates of closely packed, thin-walled capillaries, usually blood-filled and lined by a flattened endothelium, separated by scant connective tissue stroma The lumens may be partially or completely thrombosed and organized. Rupture of vessels causes scarring and accounts for the hemosiderin pigment occasionally found.

Cavernous Hemangioma.

Less common than the capillary variety, cavernous hemangiomas are distinguished by the formation of large, dilated vascular channels. Although they share age and anatomic distribution, they are usually larger, are less circumscribed, and more frequently involve deep structures than capillary hemangiomas.

MORPHOLOGY.

Grossly the usual cavernous hemangioma is a red-blue; soft, spongy mass 1 to 2 cm in diameter. rarely, giant forms occur that affect large subcutaneous areas of the face, extremities, or other regions of the body. Histologically the mass is sharply defined but not encapsulated and made up of large, cavernous vascular spaces, partly or completely filled with blood separated by a scant connective tissue stroma.

In most situations, hemangiomas are of little clinical significance; however, they can be a cosmetic disturbance owing to their vulnerability to traumatic ulceration and bleeding. Moreover, when picked up in internal organs by computed tomography or magnetic resonance imaging scans, they must be differentiated from more ominous lesions. Those in the brain are most threatening, since they may cause pressure symptoms or rupture.

Pyogenic Granuloma :.

Pyogenic granuloma is a polypoid form of capillary hemangioma that occurs as a rapidly growing exophytic red nodule attached by a stalk to the skin and gingival or oral mucosa, which bleeds easily and is often ulcerated. Perhaps one third of lesions develop after trauma, growing rapidly to reach a maximal size of 1 to 2 cm within a few weeks. The proliferating capillaries are often accompanied by extensive edema and an acute and chronic inflammatory infiltrate, especially when ulcerated, yielding a striking resemblance on histologic examination to exuberant granulation tissue and sometimes suggesting an infectious cause. Recurrence occurs infrequently as a solitary nodule or as satellite nodules. Pregnancy tumor (granuloma gravidarum) is a pyogenic granuloma occurring in the gingiva of 1% of pregnant women that regresses after delivery. These lesions, similar to the spider telangiectasias discussed subsequently, emphasize the yet poorly understood role of estrogen in vascular growth and proliferation under certain circumstances.

Lymphangioma

Lymphangiomas are the lymphatic analogue of the hemangiomas of blood vessels.

Simple (Capillary) Lymphangioma.

Simple (capillary) lymphangiomas are masses, composed of small lymphatic channels, that tend to occur subcutaneously in the head and neck region and in the axilla.

Cavernous Lymphangioma (Cystic Hygroma).

These benign lymphatic tumors are composed of cavernous lymphatic spaces and therefore are analogous to the cavernous hemangioma. Almost invariably occurring in children in the neck or axilla and only rarely retroperitoneally, they occasionally achieve considerable size, up to 15 cm in diameter. Such large masses may fill the axilla or produce gross deformities in and about the neck. The tumors are made up of massively dilated cystic spaces lined by endothelial cells and separated by a scant intervening connective tissue stroma, which often contain lymphoid aggregates. The margins of the tumor are not discrete, and these lesions are not encapsulated. Their removal can therefore be difficult.

Angiosarcoma (malignant tumor):

Angiosarcomas are malignant endothelial neoplasms with structure varying from highly differentiated tumors to those whose anaplasia makes them difficult to distinguish from malignant epithelial neoplasms. They occur in both sexes and more often older adults anywhere in the body but most often in the skin, soft tissue, breast, and liver.

Angiosarcomas may also arise in the setting of lymphedema, most typically approximately 10 years after radical mastectomy for breast cancer. In such cases, the tumor presumably arises from dilated lymphatic vessels (lymphangiosarcomas). Clinically the edematous arm may undergo acute swelling followed by the appearance of subcutaneous nodules, hemorrhage, and skin ulceration. The nodules are frequently multiple, but they later become confluent, forming a large mass. Angiosarcomas may also be induced by radiation in the absence of lymph edema.

MORPHOLOGY.

Grossly, cutaneous angiosarcoma may begin as deceptively small, sharply demarcated, asymptomatic, often multiple red nodules, but eventually most angiosarcomas become large, fleshy masses of pale gray-white soft tissue. The margins blend imperceptibly with surrounding structures. Central softening and areas of necrosis and hemorrhage are frequent.

Microscopically, all degrees of differentiation of these tumors may be found, from those that are largely vascular with plump, anaplastic but recognizable endothelial cells producing vascular channels to tumors that are quite undifferentiated produce no definite blood vessels, and are markedly atypical. The more malignant variant tends to have a solid spindle cell appearance.

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Dr. Ali Zeki

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