Hepatocellular carcinoma after transcatheter hepatic arterial embolization. A histopathologic study of 84 resected cases.

Background: Recently, transcatheter arterial embolization (TAE) has been used to treat hepatocellular carcinoma (HCC), yet much is still unknown regarding its optimal use.
Methods: Eighty-four patients with HCC after TAE underwent surgical resection. Fifty of the tumors were less than 3 cm (small HCC [S-HCC]), and 34 were 3 cm or larger (large HCC [L-HCC]). Necrosis rate, distribution of residual HCC, histopathology of the main tumor, and proliferating activity of residual HCC by means of proliferative cell nuclear antigen (PCNA) were examined. Twenty-two randomly selected patients with HCC treated with standard chemotherapy were used as non-TAE control subjects.
Results: A necrosis rate of greater than 95% was seen in 35 cases of S-HCC and in 15 of L-HCC. All five nonencapsulated tumors were L-HCC and had a much lower necrosis rate. No tumors in the control group showed a necrosis rate of greater than 95%. Encapsulated tumors were categorized according to their tumor interiors, capsules, and extracapsular zones. Complete necrosis of the tumor interior was 80.0% and 35.3% in S-HCC and L-HCC, respectively. Viable residual tumors were found mainly in the extracapsular zone in S-HCC, whereas in L-HCC they were located primarily in the tumor interior. Most capsules were affected by tumor necrosis and the subsequent healing process, resulting in a thick secondary capsule. Tumor interior necrosis was uniform and coagulative in S-HCC, in contrast to L-HCC, in which necrotic regions comprised several necrosis units of differing texture and were divided by fibrous septa. In contrast, the control group revealed spotty, sparse necrosis. Non-TAE tumor capsules were thin and pathologically characteristic of those naturally occurring in tumors, as opposed to the thick fibrous capsules, which are inducible by TAE therapy. In the TAE group, the PCNA positivity rates were 37.5%, 52.5%, and 100% in Grades 1, 2, and 3/4 combined, respectively. At the tumor-nontumor boundary of the extracapsular region, PCNA-positive cells were detected in 55.0% of the cases.
Conclusions: The thickened tumor capsule serves as a good postoperative indicator of TAE response. Small tumors seem to be affected in the tumor interior, whereas extracapsular invasion undermines the TAE effect. PCNA was helpful in detecting the tumor-nontumor boundary and useful as a parameter of viability of HCC after TAE.