Programmed cell death ligand 1 expression associated with subtypes of post-transplant lymphoproliferative disorder among pediatric kidney transplant recipients.

BACKGROUND: Programmed cell death ligand 1 (PD-L1) expression on tumor cells engages the PD-1 receptor on T cells, inhibiting anti-tumor responses. PD-L1 has been detected in cases of post-transplant lymphoproliferative disorder (PTLD) but reports are limited. Here we examine PD-L1 expression and evaluate for clinical correlations. METHODS: Twenty-one cases of PTLD were identified among pediatric kidney transplant recipients at our institution from February 1996 to April 2017. Using paraffin-embedded tissue biopsies, we examined 21 primary tumors for expression using PD-L1 monoclonal antibody performed with PAX5 as a double stain. We scored expression of PD-L1 on lesional B-cells as a percentage of positive cells. Clinical course and outcome were obtained from retrospective chart review. RESULTS: Applying revised 2017 WHO PTLD classification showed five non-destructive, nine polymorphic, and seven monomorphic cases. Average PD-L1 expression based upon PTLD subtype was: non-destructive 11%, polymorphic 43%, and monomorphic 73% (p = .01). Two patients transferred shortly after diagnosis, five received chemotherapy, and three died from PTLD. Among the fatalities, all showed monomorphic PTLD and 90% of lesional B-cells expressed PD-L1. CONCLUSION: In this case series, significant differences in PD-L1 expression were seen among different subtypes, and monomorphic PTLD demonstrated the highest expression. Study of a larger cohort is needed, and if the correlation of PD-L1 expression and PTLD subtype is confirmed, this may highlight the potential utility of checkpoint inhibitor therapy in cases of severe or refractory disease among kidney transplant recipient in whom the risk of allograft loss is acceptable given the option of chronic dialysis.

Tissue expander-stimulated lengthening of arteries for the treatment of midaortic syndrome in children.

BACKGROUND: Midaortic syndrome (MAS) is a rare condition characterized by stenosis of the abdominal aorta. Patients with disease refractory to medical management will usually require either endovascular therapy or surgery with use of prosthetic graft material for bypass or patch angioplasty. We report our early experience with a novel approach using a tissue expander (TE) to lengthen the normal native arteries in children with MAS, allowing primary aortic repair without the need for prosthetic graft material. METHODS: We conducted a retrospective review of patients with MAS undergoing the TE-stimulated lengthening of arteries (TESLA) procedure at our institution from 2010 to 2014. Data are presented as mean (range). RESULTS: Five patients aged 4.8 years (3-8 years) underwent the TESLA procedure. Stages of this procedure include the following: stage I, insertion of retroaortic TE; stage II, serial TE injections; and stage III, final repair with excision of aortic stenosis and primary end-to-end aortic anastomosis. Stage II was completed in 4 months (1-9 months) with 12 (7-20) TE injections. Goal lengthening was achieved in all patients. Stage III could not be completed in one patient because of extreme aortic inflammation, which precluded safe excision of the aortic stenosis and required use of a prosthetic bypass graft. The other four patients completed stage III with two (one to three) additional vessels also requiring reconstruction (renal or mesenteric arteries). At 3.2 years (1-6 years) of follow-up, all patients are doing well. CONCLUSIONS: The TESLA procedure allows surgical correction of MAS without the need for prosthetic grafts in young children who are still growing.