sentences:  Though these lesions may resemble nodular melanoma, the lack of induration, slow growth, and lightening appearance upon diascopy suggest against it, and indicate a vascular lesion.Additionally, lack of pulsation distinguishes this lesion of the lower lip from a tortuous segment of the inferior labial artery.The cause is unknown; however it is thought to be associated with sun exposure, leading to a dilated blood-filled vascular channel "...lined with a singled layer of flattened endothelial cells and a thin wall of fibrous tissue filled with red blood cells."