The primary tubal serous borderline tumor is a very rare neoplasm of the fallopian tube. We present a case of the tubal serous borderline tumor diagnosed using the HDlive Flow silhouette with the glass-body rendering mode. Two-dimensional sonography showed a left-sided sausage-shaped cyst with low-level echoes and several mural papillae. Radiant Flow demonstrated a few penetrating intratumoral blood vessels within papillary projections. HDlive depicted a typical torturous shape of the left hydrosalpinx and several irregular papillae. The HDlive Flow silhouette with the glass-body rendering mode clearly showed numerous penetrating vessels at the base of irregular papillary projections. These findings suggest borderline tumor of the left fallopian tube. The HDlive Flow silhouette with the glass-body rendering mode provides an additional diagnostic clue for the preoperative diagnosis of a serous borderline tumor of the fallopian tube.