Clear cell morphology can be seen in a wide range of renal epithelial neoplasms including clear cell renal cell carcinoma (CCRCC), clear cell papillary renal cell tumor (CCPRCT), papillary renal cell carcinoma (PRCC), multilocular cystic renal neoplasm of low malignant potential (MCRNLMP), “MiT family” translocation renal cell carcinomas, renal cell carcinomas with fibromyomatous stroma. Except for “MiT family” translocation renal cell carcinoma and renal cell carcinomas with fibromyomatous stroma, most of the above-mentioned tumors can be frequently diagnosed on pure histologic basis. In challenging cases, particularly in limited samples and metastatic settings, a panel of immunohistochemical stains (i.e., PAX-8, CA-IX) can provide adjunctive diagnostic support.

A number of investigators (including our group [1]) have studied the diagnostic utility of various immunohistochemical stains such as CA-IX and CK7 in various types of clear cell renal neoplasms. The utility of Alpha-methyl CoA racemase (AMACR) in PRCC and “MiT family” translocation renal cell carcinoma is well investigated. However, the literature on AMACR reactivity in clear cell renal cell tumors has shown varying and conflicting results [2,3] (except for CCPRCT, which is either negative or focally staining [[4], [5], [6]]).

The aim of this study was to investigate AMACR immunoreactivity within the spectrum of clear cell renal cell neoplasms including low- and high-grade CCRCC, CCRCC with cystic changes, and MCRNLMP (Fig. 1).