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Soft tissue tumors

Vascular tumors

Normal vessels

Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 24 February 2013, last major update November 2012
Copyright: (c) 2003-2013, PathologyOutlines.com, Inc.

Definition
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● Normal vessels contain endothelial cells facing lumen and pericytes, smooth muscle cells and glomus cells towards outside of vessel

Embryology
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● Development begins with formation of hemangioblasts, which organize in blood islands in yolk sac, and differentiate into hematopoietic and angioblastic cells
● Hematopoietic cells generate blood cells; angioblastic cells generate vascular endothelial cells (ECs)
● Notch signaling pathway helps determine arterial program of both endothelial and smooth muscle cells (Stem Cells Int 2012;2012:805602)
● See also Development 2011;138:4569, Int J Dev Biol 2011;55:419

Normal histology
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● Vascular layers are outer tunica adventitia, intermediate tunica media and inner tunica intima; thickness depends on size and type of vessel
● Tunica adventitia: longitudinally arranged collagen; layer is larger in veins than arteries
● Tunica media: concentrically arranged smooth muscle whose diameter is altered by autonomic control; smooth muscle may secrete collagen, elastic fibers, elastic lamellae and proteoglycans; larger diameter in arteries than veins of similar size
● Tunica intima: inner endothelium and variable outer subendothelial connective tissue
● Capillaries: no muscular layer or elastic lamella; endothelial layer is complete, with pericytes present but difficult to identify on H&E
● Glomus cells: (a) modified smooth muscle cell with indistinct borders, pale cytoplasm, uniform nuclei; surround arterial segment of glomeriform arteriovenous anastomosis, which is richly innervated by autonomic nervous system fibers; or (b) peripheral chemoreceptor in carotid body and aortic body that detects hypoxia (Novartis Found Symp 2006;272:54); large, epithelioid cells with abundant cytoplasm and membrane bound, electron dense granules; richly supplied with nerve endings, see diagram below
● Pericytes: relatively undifferentiated cell that regulates microvascular blood flow (Histol Histopathol 1991;6:269, Microvasc Res 2009;77:235)
● References: University of Ottawa, Southern Illinois University, Victoria College

Diagrams
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Glomus cell	Arterial wall	Pericyte and endothelial interactions	Pericyte and endothelial interactions

Aging related changes
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● Normal vascular structure changes during life, with progressive arterial stiffness
● Capillaries: basement membrane thickens with aging

Micro images
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Small arteries	Small arteries	Small artery and vein	Capillaries
Artery #1: H&E	#2: elastin	#3: trichrome	Arteriole

Venous wall

Pericytes

Artery wall: blue arrow is tunica intima; black bracket is tunica media; green bracket is tunica adventitia

Positive stains
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● Vascular endothelium: CD34, CD31, Factor VIII related antigen, vimentin, Ulex europaeus I lectin (binds to alpha-L-fructose compounds), endothelin, von Willebrand factor; also FLI-1 (nuclear stain, Am J Surg Pathol 2001;25:1061)
● Lymphatic endothelium: similar staining as vascular endothelial cells but also D2-40+, LYVE1+, and only weakly Factor VIII related antigen+
● Pericytes: alpha smooth muscle actin, myosin, vimentin; also CD31
● Smooth muscle cells: actin, desmin

Electron microscopy description
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● Endothelial cells: cells are jointed by tight, adherans or gap junctions; numerous pinocytotic vesicles, cytoplasmic microfilaments, microvilli, continuous basal lamina and Weibel-Palade bodies (membrane bound organelle which contains von Willebrand factor)
● Capillary endothelium: surrounded by basement membrane which contains pericytes, in contrast to lymphatic endothelium which contains little basement membrane

Electron microscopy images
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Brain capillary with endothelial cells and pericyte	Weibel-Palade bodies	Endothelial junctions
Endothelial tight junction	Pericytes	Pericytes

End of Soft tissue tumors > Vascular tumors > Normal vessels

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