Clear Cell Renal Cell Carcinoma With Lipocyte-Like Features in a Multifocal Renal Tumor: Possible Morphological Sign of Tumor Regression?

We report a rare occurrence of clear cell renal cell carcinoma (RCC) with an unusual morphology resembling white adipose tissue. To the best of our knowledge, clear cell RCC exhibiting lipocyte-like morphology has been documented only once in the literature, in a report from 1996. In this study, we present a comprehensive analysis of the histological and immunohistochemical characteristics, highlighting the differences from conventional clear cell RCC. We focus on its unusual morphology and explore potential biological explanations, hypothesizing that it may represent a histologic pattern associated with tumor regression. Recognizing this morphology is important not only for expanding the spectrum of RCC growth patterns but also for diagnostic purposes, particularly in needle-core biopsy specimens. Furthermore, the characterization of the immunological microenvironment of this tumor could increase our understanding of the biological processes underlying clear cell RCC regression.