Answer: Lobular capillary hemangioma (pyogenic granuloma)

Histology: In the deep reticular dermis, one sees a well circumscribed lobulated collection of thin walled vessels in a fibrotic stroma. The epidermis is unremarkable. Nuclear atypia and mitoses are not seen.

Discussion: Pyogenic granuloma is a benign, reactive vascular proliferation which occurs in response to trauma. It is commonly seen on the head and neck or distal extremities. It is not uncommon in the pediatric population and gingival lesions can occur in pregnancy. Clinical presentation is usually that of a juicy, erythematous, friable papule or nodule that bleeds easily. They can occur deep within the skin and have a violaceous color, which may be mistaken for melanoma. Histologically, they typically occur in the papillary dermis, but they can occur in the reticular dermis or intravascularly. The lesion has a well circumscribed collection of thin walled capillaries that can take on a lobulated appearance. Superficial lesions have a collarette of scale. The surrounding stroma may have a myxoid and edematous appearance with occasional mast cells and stellate fibroblasts. Fibrosis may be seen in involuting lesions. Angiosarcoma would show a poorly formed vessels dissecting between collagen fibers in the dermis with prominent nuclear atypia and mitoses. Intravascular papillary endothelial hyperplasia would not show such well formed vessels and can be associated with a thrombus within a larger vessel. A solitary fibrous tumor shows a proliferation of spindle cells in a pattern-less pattern associated with staghorn vessels.