Pyogenic granuloma (PG) is a vascular endothelial growth factor (VEGF)-related neoangiogenic process. Minor trauma, chronic irritation, certain drugs and pregnancy may favor PG. Viral triggers have not been reported up to date. A 52-year-old woman with hairy-cell leukemia presented because of a 3-month history of a giant pseudotumoral lesion on her left cheek. All prior antibacterial, antifungal and anti-inflammatory treatments had failed. Histology revealed PG with sparse and isolated epithelial cell aggregates. Immunohistochemistry (IHC) identified herpes simplex virus type-I (HSV-I) antigens in the nuclei and cytoplasm of normal-appearing as well as cytopathic epithelial cells, suggesting a chronic, low-productive HSV infection. No HSV-I signal was evidenced in the endothelial cells of the PG. Furthermore, IHC revealed VEGF in the HSV-I infected epithelial cells as well as within the PG endothelial cells. These results incited oral treatment with valaciclovir, and the PG promptly resolved after 2 weeks. These findings suggest that a chronic HSV-I infection might play an indirect, partial role in neoangiogenesis, presumably via HSV-I infection-related stimulation of keratinocytic VEGF production.