Renal cortical neoplasms in long term survivors of solid organ transplantation

Background. Renal cortical neoplasms have been reported after organ transplantation, but the level of risk as well as the histological features are poorly defined. Methods. A retrospective autopsy-based study was performed to evaluate renal neoplasms occurring in patients who underwent solid organ transplantation, died, and received an autopsy from 1981 to 1997 (383 liver, 125 heart, 52 lung, 39 heart/lung, 98 kidney, 4 bowel). Patients were divided into those with short (less than 101 days), medium (101 days to 5 years), and long-term survival (more than 5 years). The control group consisted of hospital autopsies on nontransplanted patients from the odd-numbered years, 1983 through 1997. Results. Renal cortical neoplasms were identified in 32/1325 of nontransplanted patients and 15/701 transplanted patients. In transplanted patients, neoplasms were identified in 14 native and 1 allograft kidney: 2/391 in short-term survivors, 3/234 in medium, and 10/76 in long term survivors. While transplant patients with short and medium length survival had no increased risk for neoplasms, patients with long-term survival showed a 9-fold increase in cortical neoplasms. Transplant patients with neoplasms averaged 47 years of age at death, significantly younger than the average age of 70 for nontransplanted control patients with renal neoplasms. The neoplasms in transplanted patients were all tubulopapillary, except for one clear cell neoplasm and ranged in size from 0.1 to 2 cm. Conclusions. Long-term survivors of solid organ transplants have an 9-fold increased risk of developing tubulopapillary renal cortical neoplasms. Small renal cortical epithelial neoplasms have long been at the center of a debate on their proper classification: are they adenomas or small carcinomas? Initially, a “3-cm rule” was used by some to separate adenomas from small carcinomas (1). However, a number of reports documented metastases from lesions less than 3 cm making this rule problematic. Currently, one recommendation for the diagnosis of renal adenomas is based on size (less than 5 mm), architecture (papillary or tubulopapillary), and histology (no resemblance to clear cell, chromophobe, or collecting duct carcinoma) (2). Others have recommended that the diagnosis of adenoma should be based on cytogenetic findings (3, 4). In this study, these epithelial neoplasms of uncertain malignant potential will be referred to as renal cortical neoplasms. Factors associated with an increased risk for renal cortical neoplasms include age, sex, smoking, ateriolonephrosclerosis, and acquired cystic renal disease (2, 5, 6). Although generally considered to have limited malignant potential, renal cortical neoplasms may be of greater clinical significance in certain high risk groups. For example, an increased risk for renal cell carcinomas, predominately of the papillary type, has been documented in the majority of studies on patients with acquired cystic renal disease (7) and small tubulopapillary renal cortical neoplasms may be the immediate precursors of these papillary renal cell carcinomas (8, 9). Renal cell carcinomas have also been noted in some studies of solid organ transplant patients (10, 11), in particular renal transplant patients (12‐15), but the frequency of renal cortical neoplasms and the level of increased risk remains incompletely defined in the solid organ transplant population. Previous work at the University of Pittsburgh Medical Center had noted an increased frequency of renal cortical neoplasms in autopsied solid organ transplant patients who had survived for more than 5 years (16). With this background, we undertook a retrospective study of autopsied transplant patients to (1) determine the frequency of renal cortical neoplasms (2), define the level of risk for renal cortical neoplasms, and (3) characterize the histological features of renal cortical neoplasms in this patient population.