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The classification of urothelial neoplasms of the kidney traditionally has been similar to that of urinary bladder tumors. Several years ago, the classification of papillary urothelial neoplasms was revised. The current study focuses on the application of the 1998 World Health Organization (WHO)/International Society of Urological Pathology classification system to 102 renal pelvic urothelial neoplasms and compares it to the 1973 WHO classification scheme. In this study, all tumors were classified as urothelial carcinomas, and the majority (85%) were papillary. Most patients with papillary tumors presented with 'superficial' disease (rpT1). With the 1998 system, most papillary carcinomas were high grade, and were more often invasive as compared to low-grade tumors. Only 34% were low-grade papillary tumors and, of these, most (93%) were noninvasive. With the 1973 system, most papillary tumors were grade 2 or 3, with invasion more common in grade 3 tumors. By 1973 criteria, grade 2 tumors were a heterogeneous group; with 1998 criteria, nearly one-half were high grade and the other half low grade. The grade of papillary urothelial carcinomas with both the 1973 and 1998 grading methods was associated with stage (P ¼ 0.001). Our study reveals that papillomas and papillary urothelial neoplasms of low malignant potential are uncommon tumors in the kidney. Renal pelvic papillary urothelial neoplasms are most often carcinomas and are more commonly high grade than low grade. Although both the 1973 and 1998 systems showed a significant association with tumor stage, grade 2 papillary carcinomas are a heterogeneous group by 1973 criteria. The 1998 system provides useful information in that it more clearly defines a papillary tumor's grade and selects for a group of tumors, namely low-grade papillary urothelial carcinomas, for which a low likelihood of invasion can be predicted.

Posttransplant lymphoproliferative disorders define an important form of lymphoproliferative disease causally linked with a state of iatrogenic immune dysregulation inherent to the posttransplant setting. Most posttransplant lymphoproliferative disorders are in the context of Epstein-Barr virus-associated B-cell lymphoproliferative disease, most notably diffuse large-cell B-cell lymphoma. A less common variant falls under the rubric of posttransplant T-cell lymphoproliferative disease, which is largely unrelated to Epstein-Barr virus infection. Anaplastic large-cell lymphoma (ALCL) is the most recognized form of posttransplant T-cell lymphoproliferative disease. Although the 6p25.3 translocation is seen in a variety of B-cell lymphoproliferative disorders, this particular translocation in the spectrum of T-cell lymphoproliferative disease is a fairly specific finding pointing toward a diagnosis of primary cutaneous ALCL and a rare subset of lymphomatoid papulosis. This translocation in the peripheral T-cell lymphoma setting serves as a favorable prognostic predictor. We report a case of an 81-year-old heart transplant recipient who developed an expansile neck mass 17 years after his heart transplant. A diagnosis of cutaneous ALCL was subsequently made with cytogenetic analysis yielding the 6p25.3 translocation. The characteristic biphasic morphology of a small-cell epidermotropic neoplastic cell populace in concert with a dermal based large-cell infiltrate characteristic for those cases of ALCL harboring this translocation was seen. After excision of the nodule, his azathioprine was withheld. He is currently alive and well without evidence of disease.