Density and breast cancer risk.

Many medical terms currently in use are not included in the International Classification of Diseases of the WHO but are widely accepted because they define a specific problem or scenario in clinical practice and can be used to help guide appropriate management. AML with minimal fat is such a term. The presence of visible fat at imaging has served as a practical guide for avoiding surgical intervention for suspected renal cancers. Yet, the absence of visible fat at imaging is more ambiguous and leads to unnecessary surgeries (1). We agree that AML should be the preferred term for pathologic reports, irrespective of the amount of fat in the lesion. We believe that applying the WHO classification for AMLs to imaging reports creates gaps in the context of guiding clinical practice. Although most urologists are quite familiar with the imaging appearance and description of “classic” AMLs, the imaging features of AMLs containing minimal fat are probably not as widely recognized. The use of just AML in radiology reports for those masses lacking visible fat can be confusing to urologists, who expect and search for the classic appearance of a fatty mass. Milner et al (2) specifically addressed the issue of AMLs containing minimal amounts of fat on imaging studies, as the title of their article indicates. In their article, “fat poor cases were defined as the failure of preoperative imaging to demonstrate fat within a lesion, thus making it unsuspected at surgery done for presumed renal cell carcinoma due to an enhancing mass” (2). In the Results section, the authors indicated that, with this definition, 92% of the AMLs without visible fat at imaging had less than 25% fat per high-field-strength power at histopathologic examination. It is based on this important observation that we defined the histopathologic criteria in our study. In this regard, our approach was based on objective data and validates the results of Milner et al. The term AML with minimal fat may not be recognized by the WHO, but its use reflects the pathologic findings and can avoid misinterpretations in everyday clinical practice. This approach is analogous to the use of the term lipid-poor adenoma, which is applied to a subset of adrenal adenomas without detectable lipid content at imaging and widely accepted in the medical and surgical literature (3,4). The term is practical in the context of clinical practice because it can facilitate appropriate management decisions.