Mast cells in infantile haemangioma possess a primitive myeloid phenotype.

AIMS: Recent reports on infantile haemangioma (IH) have demonstrated a primitive population of interstitial cells expressing the embryonic transcription factor, Nanog, with decreasing abundance during involution. In this report we investigated the expression of Nanog on mast cells in all three phases of IH progression. METHODS: Paraffin-embedded sections of six proliferating, six involuting and six involuted IH lesions were used to investigate the expression of tryptase, Nanog, CD45, CD34 and GLUT-1 by immunostaining. RESULTS: Mast cells, identified by their expression of tryptase, were located in the interstitium of IH lesions. 93%, 42% and 0% of these tryptase(+) cells also expressed Nanog, in proliferating, involuting and involuted IH, respectively. CONCLUSIONS: The identification of an abundant population of tryptase(+)/Nanog(+) cells in IH is novel. The relative loss of Nanog expression as IH involutes may be a result of maturation and/or proliferation of these cells. This report supports the primitive nature of IH.

Verrucous hemangioma expresses primitive markers.

BACKGROUND: Verrucous hemangioma (VH) presents clinically as a vascular malformation but has similar histopathologic features to infantile hemangioma. This study characterized the cell population within VH. MATERIAL AND METHODS: Paraffin-embedded sections from two male patients with VH were processed for immunohistochemistry. The expression of SMA, CD34, glucose transporter-1 (Glut-1), D2-40, brachyury, angiotensin converting enzyme (ACE), Oct-4, hemoglobin ζ chain (HBZ), Wilms tumor protein (WT-1) and CD45 was examined. RESULTS: The lymphatic marker, D2-40, was not expressed in VH, whereas Glut-1 was widely expressed in infantile hemangioma, it was only focally expressed by the endothelium of VH. The endothelium of VH expressed the primitive markers, Oct-4, brachyury and ACE. The primitive marker, WT-1, was expressed predominantly on the pericyte layer of both VH and infantile hemangioma. However, HBZ was only expressed in infantile hemangioma. CD45, a mature hematopoetic marker, was expressed by cells within the interstitium, away from the endothelium of VH and infantile hemangioma. DISCUSSION: The expression of the primitive markers, Oct-4, brachyury and ACE on the endothelium, and WT-1 predominantly on the pericyte layer of VH shows a primitive microvascular phenotype similar to infantile hemangioma. However, the absence of the embryonic marker, HBZ, expressed only in first trimester placenta and in proliferating infantile hemangioma, suggests a different cellular origin. HBZ could be used to distinguish between the two conditions.