lobular capillary hemangioma, superficial

LOBULAR CAPILLARY HEMANGIOMA THAT IS MOSTLY SUPERFICIAL (PYOGENIC GRANULOMA)

The common term pyogenic granuloma is a total misnomer in that such lesions are neither pyogenic nor granulomata. It is only after such a lesion ulcerates that superficial infiltrates of polymorphonuclear leukocytes appear, and at no stage are granulomatous histiocytic infiltrates a feature. Such lesions represent a proliferation of vascular elements, often in an explosive manner. Therefore terms such as lobular capillary hemangioma, eruptive hemangioma, and pyogenic granuloma type of hemangioma are preferred.

A striking expansion of the papillary dermis by capillaries lined by endothelial cells and associated with pericytes is characteristic of most lobular capillary hemangiomas (LCH). A few capillaries having branching outlines may be seen, particularly in older lesions. There are examples of LCH wherein these elements not only involve the papillary dermis but also the reticular dermis, and there are cases where the proliferating vascular elements are restricted to the subcutis or deep reticular dermis. Intravascular LCH's occur (so-called intravascular pyogenic granulomas).

The lobular nature of LCH is best seen in early lesions. In fact, the characteristic lobular architecture may no longer be apparent in late lesions. Fibrosis, which can be interpreted as partial regression, appears in many LCH's that are not treated.

Feeder vessels can be demonstrated in the reticular dermis in most cases of LCH, and the role of these vessels in the formation of LCH is the basis of fascinating speculation. These vessels have thicker walls than the vessels that normally should be found in the middle of the reticular dermis, and there are spindle cells having the features of smooth muscle in the walls of such vessels. These vessels may be tortuous or have kinked outlines. Hyperplasia of perivascular fibroblasts is sometimes seen, and the peripheral collagen may be glassy or hyalinzed, particularly in the reticular dermis component. Lobules composed of endothelial cells and pericytes may be found in close proximity to the feeder vessels. This relationship is best demonstrate within the relatively rigid reticular dermis and within early lesions. Whether these feeder vessels represent the remnant of a subtle pre-existing vascular malformation, or whether these are formed de novo, or whether these are acquired extensions from underlying vessels can be food for thought. The fact that some LCH's recur following superficial ablation during the active growth phase provides indirect evidence that the feeder vessels may be the source of the endothelial cells and pericytes in the recurrent superficial lesion.

In view of the above, it would appear that LCH's represent a panhyperplasia of vascular and perivascular components.

This bright red papule appeared suddenly on a 14 year old male.

Scan power view. Note the marked expansion of the papillary dermis and collarette formation by lobular collections of vascular elements. There are a few similar lobules in the superficial reticular dermis.

High power view from the area in the red rectangle. Numerous vascular spaces are lined by endothelial cells. There are plump spindle cells between the vascular lumina, and these cells have the features of pericytes.

Medium power view from the area in the yellow rectangle. This vessel is abnormally thick for this location, and it has a kinked outline. Smooth muscle is in the wall of the vessel. Perivascular fibroplasia is seen. There is an erector pili muscle incidentally beneath the vessel.

High power view from the area in the black rectangle. A very early lobule composed of endothelial cells and pericytes is being formed in close proximity to a feeder vessel. Part of the periphery of the lobule has a glassy or hyalinized appearance.There is a transition in morphology from smooth muscle cells to pericytes. Hyperplasia of perivascular fibroblasts is also seen.

Click on your browser's 'Back' button to return to the previous page.

	Scan power view. Note the marked expansion of the papillary dermis and collarette formation by lobular collections of vascular elements. There are a few similar lobules in the superficial reticular dermis.
	High power view from the area in the red rectangle. Numerous vascular spaces are lined by endothelial cells. There are plump spindle cells between the vascular lumina, and these cells have the features of pericytes.
	Medium power view from the area in the yellow rectangle. This vessel is abnormally thick for this location, and it has a kinked outline. Smooth muscle is in the wall of the vessel. Perivascular fibroplasia is seen. There is an erector pili muscle incidentally beneath the vessel.
	High power view from the area in the black rectangle. A very early lobule composed of endothelial cells and pericytes is being formed in close proximity to a feeder vessel. Part of the periphery of the lobule has a glassy or hyalinized appearance.There is a transition in morphology from smooth muscle cells to pericytes. Hyperplasia of perivascular fibroblasts is also seen.