A case of hepatocellular carcinoma with pseudoaneurysm formation upon lenvatinib administration.

A 79-year-old man received treatment for multiple intrahepatic hepatocellular carcinoma with atezolizumab + bevacizumab. However, he developed lower back pain attributed to spinal metastases upon tumor enlargement; thus, he was admitted to our hospital for a change from atezolizumab + bevacizumab to lenvatinib and radiation therapy for the spinal metastases. On the 11th day after starting lenvatinib treatment, a pulsatile aneurysm appeared in the tumor, detected using abdominal ultrasonography Micro B-flow imaging, which visualized blood flow at a high frame rate; this was diagnosed as a pseudoaneurysm. The patient refused treatment for the pseudoaneurysm; therefore, he was carefully followed up. Fortunately, the pseudoaneurysm disappeared on the 17th day. One month later, the tumor had become completely necrotic. Lenvatinib demonstrated effectiveness in inhibiting angiogenesis in the tumor, as evidenced by a decrease in tumor blood flow. This case report suggests that pseudoaneurysm formation within the tumor occurs early after the administration of lenvatinib; thus, clinicians must be aware of the potential risk of pseudoaneurysm rupture.