Dear Editor:

Traumatic neuromas (TNs), benign neoplasms that originate from Schwann cells in the peripheral nervous system, are rare but well-recognized complications of hepatobiliary procedures.^1-3 They mainly appear at sites previously exposed to surgical trauma and may result in biliary obstruction and/or ischemia. With the consideration of the magnitude of biliary and vascular interventions during liver transplant (LT), TNs are only sporadically reported^4-9 and most probably underestimated. Because they do not have specific features, imaging often fails to recognize TNs preoperatively, and they are commonly discovered only on pathologic examination. Given that TNs may lead to irreversible graft dysfunction, we analyzed all liver allografts removed at liver retransplant (re-LT) in our center to identify TNs behind indications for re-LT.

All adult patients who underwent re-LT at Merkur University Hospital (Croatia) between July 2006 and August 2019 were selected using our Histology Electronic Database. Morphologic identification of neuroma was confirmed by immunostaining using S-100 marker. Additional clinical information was obtained through patient electronic medical records. All re-LT procedures involved deceased donations.

During our study period, 1107 primary LT procedures were performed; of these, 101 adults (9.1%) underwent re-LT at least once, which involved receipt of 115 liver grafts in total. The histopathologic diagnosis of TN was found in 7 grafts removed at re-LT, corresponding to an indication rate of 6.1% for liver re-LT in our institution.

Pathologic reports revealed 15- to 30-mm hap­hazard nerve proliferations within scar tissue, which were surrounding or located within the bile duct wall or hepatic artery (Figure 1). Reports also showed cholestasis and ischemic-type biliary lesions and/or advanced fibrosis, portal venous thrombosis, and hepatic artery thrombosis (HAT) with ischemia (Table 1). Six patients had duct-to-duct biliary anastomosis, and 1 had hepaticojejunostomy. Initial manifestation in most cases was jaundice and/or cholangitis; only 1 patient with HAT presented with abdominal discomfort without jaundice. In all cases, preoperative imaging failed to detect neuroma. Four patients (with HAT, cirrhosis/portal vein throm­bosis, or ischemic-type biliary lesions) had no other interventions before re-LT, whereas the others had multiple procedures. These included 1 patient with hepaticojejunostomy and its revision, 1 patient with temporary biliary drainage, and 1 patient with repeated endoscopic intervention for poor graft function and recurrent cholangitis. Median time to re-LT was 30 months (range, 3-51 mo). In all patients, re-LT was successful, with good graft function at follow-up.

In the context of LT, these small benign tumors may have devastating consequences on the graft. Histologic data have shown that TNs are not uncommon (28%) after LT, although symptomatic TNs are rare (1.1%).⁴ Another study demonstrated that 3.5% of biliary anastomotic strictures are TN-related and that, in terms of treatment, endoscopic interventions are inferior to biliary reconstructions or re-LT.5 A recent single-center study on TN after LT showed a rate of incidence of 0.5%; TN was present in 9.6% of biliary anastomotic strictures specimens, and all cases occurred late after LT and only when duct-to-duct biliary reconstruction was performed.⁸

To conclude, biliary obstruction and/or perfusion abnormalities of the hepatic artery/portal vein late after LT may suggest the formation of TNs. The preoperative diagnosis of TN remains challenging due to the lack of specific imaging features. To resolve TNs, surgical modalities are mostly needed. In the clinical setting, TN-related graft loss is expected; however, finding strategies to minimize and prevent neuroma development are needed.

References:

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