Page 414 - Textbook of Pathology, 6th Edition

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Figure 15.7 Structure of a fully-developed atheroma. The opened
up inner surface of the abdominal aorta shows a variety of atheromatous
lesions. While some are raised yellowish-white lesions raised above the
surface, a few have ulcerated surface. Orifices of some of the branches
coming out of the wall are narrowed by the atherosclerotic process.

Grossly, the lesions may appear as flat or slightly elevated Grossly, atheromatous plaques are white to yellowish-
SECTION III
and yellow. They may be either in the form of small, white lesions, varying in diameter from 1-2 cm and raised
multiple dots, about 1 mm in size, or in the form of on the surface by a few millimetres to a centimetre in
elongated, beaded streaks. thickness (Fig. 15.7). Cut section of the plaque reveals the
Microscopically, fatty streaks lying under the endo- luminal surface as a firm, white fibrous cap and a central
thelium are composed of closely-packed foam cells, lipid- core composed of yellow to yellow-white, soft, porridge-
containing elongated smooth muscle cells and a few like material and hence the name atheroma.
lymphoid cells. Small amount of extracellular lipid, Microscopically, the appearance of plaque varies depen-
collagen and proteoglycans are also present. ding upon the age of the lesion. However, the following
features are invariably present (Fig. 15.8):
2. GELATINOUS LESIONS. Gelatinous lesions develop
Superficial luminal part of the fibrous cap is covered
in the intima of the aorta and other major arteries in the by endothelium, and is composed of smooth muscle cells,
first few months of life. Like fatty streaks, they may also dense connective tissue and extracellular matrix
Systemic Pathology
be precursors of plaques. They are round or oval, containing proteoglycans and collagen.
circumscribed grey elevations, about 1 cm in diameter. Cellular area under the fibrous cap is comprised by a
Microscopically, gelatinous lesions are foci of increased mixture of macrophages, foam cells, lymphocytes and a
ground substance in the intima with thinned overlying few smooth muscle cells which may contain lipid.
endothelium. Deeper central soft core consists of extracellular lipid
3. ATHEROMATOUS PLAQUES. A fully developed material, cholesterol clefts, fibrin, necrotic debris and lipid-
atherosclerotic lesion is called atheromatous plaque, also laden foam cells.
called fibrous plaque, fibrofatty plaque or atheroma. Unlike In older and more advanced lesions, the collagen in the
fatty streaks, atheromatous plaques are selective in fibrous cap may be dense and hyalinised, smooth muscle
different geographic locations and races and are seen in cells may be atrophic and foam cells are fewer.
advanced age. These lesions may develop from 4. COMPLICATED PLAQUES. Various pathologic chan-
progression of early lesions of the atherosclerosis ges that occur in fully-developed atheromatous plaques are
described above. Most often and most severely affected is the called the complicated lesions. These account for the most
abdominal aorta, though smaller lesions may be seen in serious harmful effects of atherosclerosis and even death.
descending thoracic aorta and aortic arch. The major These changes include calcification, ulceration, thrombosis,
branches of the aorta around the ostia are often severely haemorrhage and aneurysmal dilatation. It is not
involved, especially the iliac, femoral, carotid, coronary, uncommon to see more than one form of complication in a
and cerebral arteries. plaque.