Carcinoma of the collecting ducts of Bellini and renal medullary carcinoma are rare aggressive neoplasms of putative distal nephron origin. First described in 1949, case reports and review articles constitute a major source of information on collecting duct carcinoma, whereas Davis and colleagues and the pediatric tumor registry have contributed the seminal works on renal medullary carcinoma. Here we present a detailed study of collecting duct carcinoma (n=39) and renal medullary carcinoma (n=13), characterizing these rare neoplasms and analyzing their interrelationship. Both collecting duct carcinoma and renal medullary carcinoma exhibited significant similarities, such as predilection for the right kidney, tumor mass with an epicenter in the renal medulla, and a mean size of 7 cm. Overall, both tumors exhibited a poorly differentiated adenocarcinoma histology with desmoplastic stromal response (100%), inflammatory infiltrate (100%), frequent perinephric extension (collecting duct carcinoma: 97%; renal medullary carcinoma: 83%), lymphovascular invasion (100%), intraluminal mucin (collecting duct carcinoma: 42%; renal medullary carcinoma: 73%), high nuclear grade (97%), overlapping immunoreactivity for Ulex europaeus agglutinin 1 (collecting duct carcinoma: 75%; renal medullary carcinoma:55%), CK7 (collecting duct carcinoma: 44%; renal medullary carcinoma: 71%), and high–molecular weight cytokeratin (collecting duct carcinoma: 26%; renal medullary carcinoma: 29%), and nonimmunoreactivity for Ksp-cadherin. Histologically, collecting duct carcinoma frequently had tubular, tubulopapillary, or irregular glandular architecture, whereas renal medullary carcinoma commonly demonstrated islands of anastomosing tubules and cords forming irregular microcystic spaces. Multiple metastases to the lymph nodes, lung, bone, and liver were observed in both categories at presentation (collecting duct carcinoma: 17%; renal medullary carcinoma: 36%). Only patients with organ-confined small tumors were disease free beyond the median survival time. Differential clinical features between collecting duct carcinoma and renal medullary carcinoma included proclivity for younger male individuals of African ancestry with hemoglobin abnormalities and a shorter median survival of 17 weeks (vs. 44 wk for collecting duct carcinoma) for renal medullary carcinoma. The markedly overlapping clinical features, histology, immunophenotype, metastasis patterns, and uniformly aggressive outcome in collecting duct and renal medullary carcinomas suggest that renal medullary carcinoma is a distinctive clinicopathologic subtype within the entity of collecting duct carcinoma. The extremely poor prognosis and ongoing clinical trials with specific therapeutic protocols argue for their accurate distinction from other renal cell carcinoma subtypes.
*Department of Pathology and Laboratory Medicine, Cedars-Sinai Medical Center, Los Angeles, CA
‡Department of Pathology, Miraca Life Sciences, Dallas, TX
∥Department of Pathology, Grady Health System, Emory University School of Medicine, Atlanta, GA
‡‡Department of Pathology, Cleveland Clinic Foundation, Cleveland, OH
§§Department of Pathology, New York University, New York, NY
##Department of Pathology, PhenoPath Laboratories, Seattle, WA
†Department of Pathology, Faculdade De Ciencias Medicas UNICAMP, Campinas
**Department of Pathology, Consultoria em Patologia, Botucatu
††Department of Pathology, Santa Casa School of Medicine, São Paulo
∥∥Department of Pathology, Associação Mario Penna — Hospital Luxemburgo, Belo Horizonte-MG, Brazil
§Department of Pathology, Institute of Clinical Pathology, University Hospital Zurich, Zurich
¶Department of Pathology, Institute of Pathology, Kantonsspital St Gallen, St Gallen, Switzerland
#Department of Pathology, Charles University Hospital, Pilsen, Czech Republic
¶¶Department of Pathology, Portuguese Institute of Oncology, Lisbon, Portugal
Conflicts of Interest and Source of Funding: The authors have disclosed that they have no significant relationships with, or financial interest in, any commercial companies pertaining to this article.
Correspondence: Mahul B. Amin, MD, Department of Pathology and Laboratory Medicine, Cedars-Sinai Medical Center, 8700 Beverly Blvd Suite 8728, Los Angeles, CA 90048 (e-mail: email@example.com).