Can a venous leg ulcer present as a perfect round circle? Have read they are irregular.

All Shapes. Most venous ulcers are round or oval but they can present in irregular shapes also.
Yes. A venous stasis ulcer, especially small ones, can be perfectly round. A vascular surgeon is best to diagnose and treat them as they are slow to heal.
Venous ulcers. Venous leg ulcers can be regular or irregular in their borders. Usually venous ulcers are located on the medial(most common) or lateral side of the ankle and not on the foot or toes (these are usually arterial or diabetic ulcers).