In the current study, the incidence of needle-track seeding from HCC after a US-guided procedure (FNAB, PEI and PTBD) was 0.14% (7 of 5,092 patients) and the incidence of implanted nodule recurrence after surgical excision was 25% (2 of 8 patients). Two patients who had undergone only mass excision instead of en-bloc wide excision experienced the recurrence of needle-track seeding after surgical excision. One of these underwent en-bloc wide excision for the recurred implanted nodule and experienced no further recurrence of needle-track seeding during the study period.
Biliary peritonitis, intra-and extrahepatic tumor seeding, and intrahepatic hematoma are the most serious complications of PEI, FNAB, and PTBD in HCC.13
Complications after FNAB and PEI are rare, with reported incidences of 2.4% and 0.05-0.18% and mortality rates of 0.1% and 0.006-0.031%, respectively.14
However, the overall complication rate after PTBD is higher with an incidence of 3.4-5%.21
In the current study, two (0.13%) of the 1,549 patients who underwent PEI, four (0.12%) of the 3,391 patients who underwent FNAB, and one (0.66%) of the 152 patients who underwent PTBD for HCC experienced needle-track seeding. Silva et al in a systematic review and meta-analysis of eight observational studies found that the incidence of needle-track seeding after FNAB varied widely from 0-5.8%.11
As compared with previous reports, rates of needle-track seeding after PEI and FNAB were slightly lower in the current study. The number of patients in the current study was much larger than the previous observational studies, which would contribute to lower incidence in the current study due to the abundant experience.
The mechanism of needle-track seeding from HCC is probably complex and several causes have been discussed.22
In animal models, Ryd et al found that FNAB can implant 103
cells along a single needle-track.23
Tumor size and degree of histologic differentiation, number of needle passes, the difference in the number of needle passes and the obtained specimens, the thickness of liver parenchyma along needle-tracks, and needle type have all been considered factors of needle-track seeding after FNAB in HCC.24
Kim et al reported that the number of needle passes seemed to affect the frequency of needle-track seeding and suggested that the life expectancies of patients influence the frequency of needle-track seeding more significantly than the size or degree of differentiation of HCC.26
In addition, many cases of needle-track seeding after PEI have been reported.9
Di Stasi et al reported that tumoral seeding after PEI occurs for deeply located and small HCCs, but found no relation between seeding risk and HCC cytology.9
No report has been issued on the recurrence of needle-track seeding and the factors associated to the recurrence in HCC. In the current study, the recurrence rate of needle-track seeding was 25% among our eight patients at a median follow-up of 43.8 months. And we found that only the method of excision for implanted nodules was significantly associated with recurrence while other factors were not; no patients who had undergone en-bloc wide excision experienced the recurrence of needle-track seeding. Furthermore, our findings show that PTBD, like PEI and FNAB, can cause needle-track seeding.
Nevertheless, despite the risks of needle-track seeding, PEI, FNAB and PTBD are useful tools for diagnosing and treating HCC, because it appears that needle-track seeding does not exacerbate the disease course. Several studies have reported that the prognosis of needle-track seeding from HCC after PEI or FNAB is favorable and similar to that of patients who do not develop seeding, although these studies concerned clinical follow-ups on small numbers of patients.9
Despite the fact that only eight patients were included in the current study, it is the largest study conducted to date on the prognosis of needle-track seeding. In the current study, needle-track seeding, when it was treated by en-bloc side excision, did not seem to affect the long-term clinical outcome. We believe that needle-track seeding from HCC does not modify clinical course, because tumor involvement in needle-tracks appears to be limited to subcutaneous tissues at puncture sites.31
Accordingly, we believe that aggressive local ablative treatment, such as, en-bloc wide excision, can effectively remove needle-track seeding. Furthermore, the prognosis of HCC is usually not dependent on the severity of metastatic lesions, but rather on hepatic functional reserve and on the characteristics of intrahepatic lesions.32
Based on the rationale that HCC infiltrates surrounding tissues and that several needle passes are conducted, we recommend that en-bloc wide excision of implanted nodules, including surrounding tissues, should be used to treat needle-track seeding from HCC rather than mass excision. However, Takahashi et al in a report of the recurrence of needle-track seeding after wide excision suggested that needle-tract seeding is not a local, limited disease.33
Nevertheless, their patient was treated by wide excision and radiotherapy and remained alive without evidence of recurrence, which reinforces the point that aggressive local treatment is well worth considering.
The current study has some limitations that should be mentioned. First, the number of patients enrolled and the follow-up period were not enough to determine the effects of the surgical method used to treat needle-track seeding on clinical outcome. Second, one of the two patients who experienced the recurrence of needle-track seeding after surgical excision had combined hepatocellular-cholangiocarcinoma and long-term clinical outcome of this patient could not be evaluated because of loss of follow-up. Combined hepatocellular-cholangiocarcinoma is known to have a poorer prognosis than the ordinary HCC.34
In the current study, the frequency of needle-track seeding in patients with combined hepatocellular-cholangiocarcinoma was 12.5%, which is much larger than that in patients with ordinary HCC. Nevertheless, we believe that en-bloc wide excision might be also useful for the treatment of needle-track seeding in this subgroup. Further studies in this subgroup will be needed to clarify this issue.
Recently, the long term survivals of HCC patients are increasing due, in no small part, to the introductions of curative local ablation and liver transplantation. The current study shows that needle-track seeding can be curatively treated by en-bloc excision without recurrence, and that therefore, it should not be considered to be similar to systemic metastasis. Therefore our findings indicate that needle-track seeding, if it is treated by en-bloc wide excision, should not be considered as contraindication for liver transplantation.
Taken together, needle-track seeding after PEI or FNAB by HCC is a rare but important complication, and it can also occur after PTBD for biliary obstruction by HCC. However, the result of follow-up indicates that the prognosis of needle-track seeding, when it is treated by en-bloc wide excision, is favorable. Our results suggest that implanted nodules should be treated by en-bloc wide excision in cases with needle-track seeding from HCC after an US-guided procedure, especially in patients awaiting liver transplantation.