Squamous cell carcinoma in a chronically rejected renal allograft.

The malignant degeneration of a chronically rejected kidney allograft has been rarely reported. Almost invariably such malignancies originated in the transitional epithelium. We herein present the first occurrence of squamous cell carcinoma (SCC), originating from occult donor cells, in a chronically rejected renal allograft. Nearly 20 years after chronic rejection and loss of function of a cadaver renal graft, our patient developed increasing abdominal discomfort, decrease in appetite and weight loss. A CT-scan of the abdomen showed an abnormally enlarged and irregularly contoured mass at the level of the rejected allograft. Given the clinical and radiologic picture suggestive of either an infectious or intraparenchymal hemorrhagic process, a transplant nephrectomy was performed. At surgery, it was immediately evident that a malignant degenerative process had affected the graft. The histological features of the specimen were diagnostic for a well-differentiated SCC. The donor origin of the tumor was established through a DNA microchimerism assay performed on the operative specimens. The patient did well after resection of the malignancy, although he died 5 months later owing to a myocardial infarction. In summary, even several years following the transplant, the possibility of a malignancy of donor origin developing within a failed allograft should always be considered as part of the differential diagnosis in unusual post-transplant settings.