General aspects and pitfalls in liver transplant pathology

[Fluorescence confocal microscopy-complete digitization of pathology]

BACKGROUND

Fluorescence-based confocal microscopy (FCM) can be used to create virtual H&E sections in real time. So far, FCM has been used in dermato-, uro-, and gynecopathology. FCM allows the creation of a completely digitized frozen section, which could potentially replace conventional frozen sections in the future.

OBJECTIVE

The aim of the current work is to implement FCM technology as a component of fully digitized processes in the pathological workflow. For this purpose, the current use of FCM in liver transplant pathology will be extended to other disciplines such as urology and otorhinolaryngology.

MATERIALS AND METHODS

The FCM technique continues to be used prospectively on native tissue samples from potential donor livers. Conventional frozen sections are used comparatively to virtual FCM scans.

RESULTS

The data show a nearly perfect agreement for the detection of cholangitis, fibrosis, and malignancy, and a high level of agreement for, e.g., macrovesicular steatosis, inflammation, steatohepatitis, and necrosis between virtual FCM scans and conventional routine diagnostic frozen sections.

CONCLUSION

Since the availability of time- and cost-intensive frozen section diagnostics in the context of transplant pathology in continuous operation (24/7) is now only established at very few university centers in Germany due to an increasing shortage of specialists, the use of FCM could be an important building block in the current process leading towards a fully digitized pathology workflow and should thus be extended to various disciplines.

Fluorescence confocal microscopy on liver specimens for full digitization of transplant pathology

Fluorescence confocal microscopy (FCM) is a rapidly evolving tool that provides real-time virtual HE images of native tissue. Data about the potential of FCM as an alternative to frozen sections for the evaluation of donor liver specimens are lacking so far. The aim of the current study was to determine the value of FCM in liver specimens according to the criteria of the German Society for Organ Procurement. In this prospective study, conventional histology and FCM scans of 50 liver specimens (60% liver biopsies, 26% surgical specimens, and 14% donor samples) were evaluated according to the German Society for Organ Procurement. A comparison of FCM scans and conventional frozen sections revealed almost perfect levels of agreement for cholangitis (κ = 0.877), fibrosis (κ = 0.843), and malignancy (κ = 0.815). Substantial levels of agreement could be obtained for macrovesicular steatosis (κ = 0.775), inflammation (κ = 0.763), necrosis (κ = 0.643), and steatohepatitis (κ = 0.643). Levels of agreement were moderate for microvesicular steatosis (κ = 0.563). The strength of agreement between frozen sections and FCM was superior to the comparison of conventional HE and FCM imaging. We introduce FCM as a potential alternative to the frozen section that may represent a novel approach to liver transplant pathology where timely feedback is crucial and the deployment of human resources is becoming increasingly difficult.

Oil Red O-assessed macrosteatosis in liver transplant donor biopsies predicts ischemia-reperfusion injury and clinical outcome

Steatosis in donor livers is an accepted adverse prognostic factor after liver transplantation. While its semiquantitative assessment shows varying reproducibility, it is questioned as a standard method. Additionally, the influence of hepatic steatosis on ischemia/reperfusion injury (I/R injury) has not been evaluated in biopsies after reperfusion. We compared different staining and analyzing methods for the assessment of donor liver steatosis in order to predict I/R injury and clinical outcome after transplantation. To do this, 56 paired pre- and post-reperfusion liver biopsies were analyzed for macro- (MaS)/micro- (MiS) and total steatosis in cryo and permanent sections by special fat (Oil Red O or ORO) and standard stains. Computerized morphometrical analyses were compared to the semiquantitative assessment by a pathologist. I/R injury was determined histopathologically and by M30 immunohistochemistry. We found ORO to be more sensitive in detecting hepatic steatosis with higher reproducibility for MaS. Semiquantitative analyses were highly reproducible and not inferior to computerized morphometry. Categorized MaS as determined by ORO correlated with the extent of I/R injury, initial poor function, liver enzymes, and survival. Therefore fat stains like ORO are a reliable and easy method comprising significant advantages in the evaluation of hepatic steatosis and are thereby of prognostic value. Computerized analysis is a precise tool though not superior to semiquantitative analyses.

Liver Transplant Pathology: Review of Challenging Diagnostic Situations

Histopathologic assessment of allograft liver biopsies has an important role in managing patients who have undergone liver transplantation. In this review, several topics are discussed that create diagnostic problems in transplant pathology, with emphasis on pathologic features and differential diagnosis. The topics discussed are acute cellular rejection, late acute rejection (centrizonal/parenchymal rejection), chronic rejection, plasma cell hepatitis, idiopathic posttransplant chronic hepatitis, fibrosing cholestatic hepatitis, selected viral infections (cytomegalovirus, Epstein-Barr virus, and hepatitis E), and acute antibody-mediated rejection.