Abstract
In lobular capillary hemangioma (LCH), misnamed pyogenic granuloma, only sprouting angiogenesis (SA) has been considered. We assess the occurrence of intussusceptive angiogenesis (IA) in LCH and whether IA determines the specific and other focal patterns in the lesion. For this purpose, we study specimens of 120 cases of LCH, using semithin sections (in 10), immunohistochemistry, and confocal microscopy (in 20). In addition to SA, the results in LCH showed (1) intussusceptive phenomena, including pillars/folds and associated vessel loops, which encircled interstitial tissue structures (ITSs). (2) Two types of evolved loops depending on interendothelial contacts from opposite walls: (a) numerous interendothelial contacts, alternating with capillary-sized lumens (main capillary pattern of the lesion) and (b) few interendothelial contacts, wide open lumens, and intravascular transport of pillars/folds, which were arranged linearly, forming septa (focal sinusoidal-like pattern) or were irregularly grouped (focal intravascular papillary endothelial hyperplasia, IPEH-like pattern). In conclusion, we demonstrate that IA participates in synergistic interaction with SA in LCH development and that the prevalence of specific intussusceptive phenomena determines the predominant capillary pattern and associated sinusoidal hemangioma-like and IPEH-like patterns in the lesion, which suggest a role of IA as conditioner of vessel tumour/pseudo-tumour morphology.
Highlights
The two principal and complementary forms of angiogenesis in physiological and pathological conditions are sprouting angiogenesis (SA) and intussusceptive angiogenesis (IA)
A study to assess whether IA occurs in lobular capillary hemangioma (LCH) with such a different lobular capillary pattern from intravascular papillary endothelial hyperplasia (IPEH) and sinusoidal hemangioma is of interest to explain LCH histogenesis, and to contribute to the concept that variations of a common intussusceptive mechanism can condition the morphologic expression of vessel tumours/ pseudotumours
We report the participation of IA in synergistic interaction with SA in LCH and confirm several morphogenic mechanisms involved in the formation of pillars and capillary-like structures
Summary
The two principal and complementary forms of angiogenesis in physiological and pathological conditions are sprouting angiogenesis (SA) and intussusceptive angiogenesis (IA). A study to assess whether IA occurs in LCH with such a different lobular capillary pattern from IPEH and sinusoidal hemangioma is of interest to explain LCH histogenesis, and to contribute to the concept that variations of a common intussusceptive mechanism can condition the morphologic expression of vessel tumours/ pseudotumours. To reinforce this hypothesis, this study should be expanded to investigate the presence of zones with other histologic patterns in LCH. The objectives of this study are (a) to assess whether IA participates in LCH and whether there is synergistic interaction with SA, (b) to explore the coexistence of other histologic patterns in LCH lesions, and c) to establish whether the prevalence of certain intussusceptive findings determines the morphological pattern(s) in LCH
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