Key Histopathology Features of Cutaneous Acute Graft-Versus-Host Disease Can be Detected Noninvasively

BACKGROUND. Cutaneous erythema and histopathology features in patients post allogeneic hematopoietic cell transplantation (HCT) are nonspecific, making it difficult to distinguish acute graft-versus-host disease (aGVHD) from engraftment syndrome, drug reactions, viral infections, and other etiologies. Biopsies from different locations on the same patient frequently differ in aGVHD grade, and serial biopsies of a single lesion are not possible. Proper biopsy site selection, timing, and serial noninvasive microscopic monitoring may improve our understanding and management of aGVHD. In this study, we tested the feasibility of noninvasive reflectance confocal microscopy (RCM) to detect key histopathology features of cutaneous aGVHD.

STUDY POPULATION. We enrolled 11 patients with high clinical suspicion of cutaneous aGVHD, as determined by a transplant physician. In total, 16 lesions of cutaneous aGVHD-affected site were imaged by RCM (6x6 mm²en face images at four different depths) and subsequently biopsied (4x4 mm punch biopsy). 9 out of 11 patients had only skin involvement, and 2 patients had skin and gut aGVHD. 5 patients had >50% body surface area (BSA) affected, 1 had 18-50% BSA, and 5 had <18% BSA. 8 out of 11 patients required systemic corticosteroids and 3 patients received topical corticosteroids. All patients were imaged before starting treatment.

METHODS. We used a clinical confocal microscope (Vivascope 1500, Caliber I.D.), which enables real-time evaluation of epidermal and superficial dermal tissue at sub-cellular resolution. Four reflectance confocal microscopists blinded to histopathology independently evaluated the presence or absence of 18 RCM features¹. Concurrently, four dermatopathologists blinded to clinical and confocal information determined the presence or absence of 19 histopathology features, as well as the Lerner aGVHD grade. A histologic feature was determined as "present" in a lesion when marked by most experts (expert vote) or resolved by a fifth expert in case of a disagreement among four experts. The reflectance confocal microscopist vote was then correlated to the dermatopathologist expert vote for 17 overlapping features. We also evaluated the interrater variability among microscopists and among dermatopathologists.

RESULTS. The main aGVHD features by Lerner grade had > 88% correlation between RCM and histopathology: (1) basal vacuolar change, (2) presence of dyskeratotic keratinocytes, and (3) dermal inflammation. By contrast, dyskeratotic cells and inflammation at the adnexal structures had <50% correlation. This may be attributed to the fact that more adnexal structures are typically visible in the 6x6 mm² RCM horizontal tissue view compared to vertical section histopathology. We found a similar interrater variability among RCM experts (70%) and dermatopathologists (68%).

CONCLUSIONS. In this pilot study, we show that noninvasive label-free RCM of skin enables detection of the main Lerner grade features of cutaneous aGVHD. We found a similar interrater variability among reflectance confocal microscopists and among dermatopathologists who each independently evaluated the presence or absence of a list of aGVHD features. Future studies can build on this work to evaluate the feasibility of RCM to determine cutaneous aGVHD grade, as well as distinguish between rash due to aGVHD and drug reactions.

ACKNOWLEDGEMENT. This work was supported in part by Career Development Award Number IK2 CX001785 from the United Sates Department of Veterans Affairs Clinical Science R&D (CSRD) Service.

1. Saknite I, Gill M, Alessi-Fox C, Byrne M, Jagasia M, Gonzalez S, Ardigo M, Tkaczyk ER. Features of cutaneous acute graft-versus-host disease by reflectance confocal microscopy. Br J Dermatol (2019).