A pediatric and young adult case of unclassified renal cell carcinoma with medullary phenotype (RCCU-MP): Clinical course and treatment

Abstract

Renal cell carcinoma (RCC) is the most common kidney tumor in adults. RCC is rare in children, although its incidence increases in the second decade of life. Renal medullary carcinoma (RMC) is a rare and often aggressive RCC subtype characterized by complete loss of SMARCB1/INI1, predominantly diagnosed in patients with sickle cell disease or -trait. Here, we describe a pediatric and a young adult patient with clinicopathological characteristics similar to RMC but without hemoglobinopathies. These tumors are currently classified as “RCC unclassified with medullary phenotype” (RCCU-MP). Both our patients had an infiltrating, rather small kidney tumor with SMARCB1/INI1 deficiency. Remarkably, the aggressiveness and clinical course and treatment differed greatly between these two cases. So far, only nine patients, predominantly adults, have been reported. In a literature overview, most cases were metastatic and progressed or relapsed after varying treatment approaches, with low survival. Whereas the classification of these tumors remains a topic of debate, case reports add to the current knowledge of RMCs without hemoglobinopathies, stressing the importance of sharing experience concerning rare renal neoplasms with often poor outcomes, also concerning younger age categories.