Renal cell carcinoma with sarcomatoid and rhabdoid features: a clinico-pathological series of 74 cases

Objectives. Our aim is to analyze and compare the clinico-pathological features in renal cell carcinomas (RCC) with sarcomatoid and rhaboid phenotype. Material and methods. We reviewed 1,258 RCC from consecutive patients with nephrectomy from 1988 to 2015, and those with >= 1% of sarcomatoid and/or rhabdoid change were selected. They were classified as sarcomatoid or rhabdoid according with the predominant morphology, considering the global frecuency of both phenotypes as dedifferentiated component. The following variables were collected: sex, age, symptoms and existence of metastases at diagnosis, parameters listed in the protocol of renal carcinoma of the American College of Pathologists, pattern of tumor growth, perineural invasion, percentage of both tumor necrosis and characteristics of the inflammatory infiltrate. They were described by mean/median or percentage, and compared with Student-t/Mann-Whitney U or chi 2/Fisher). Results. We identified 45 RCC with sarcomatoid predominance (3,6%) and twenty-nine with rhabdoid predominance (2,3%); the first one showed a higher dedifferentiated component and perineural invasion (27.5 vs. 13.5%, p=0.003 and 28.9 vs. 3.4%, p=0.006, respectively), while the former showed a higher proportion of neutrophilic inflammation (44.8 vs. 22.2%, p=0.04) and arose more frequently over high grade RCC (55.9 us. 90.5%, p<0,001). Conclusions. There was overlapping of the clinico-pathological features of RCC with sarcomatoid and rhaboid phenotype, except for dedifferentiated component, perineural invasion and neutrophilic inflammation. This close relationship could be explained by a common underlying mechanism, the epithelial-mesenchymal transition, with a double morphological expression that, if confirmed, could lead to selecting patients that would benefit from follow-up or treatment depending on their molecular characteristics.