Tubulocystic renal cell carcinoma of the kidney: a clinical, pathological, immunohistochemical, and fluorescence in situ hybridization study

Tubulocystic renal cell carcinoma (TCRCC) is a relatively recently recognized renal neoplasm that exhibits distinct macroscopic and microscopic characteristics. Herein, we report a comprehensive study of pure TCRCC in 9 patients in which we evaluated the clinical, pathological, immunohistochemical and molecular characteristics of this disease. The patients’ ages ranged from 21 to 46 years (mean 33 years), and the ratio of men to women was 5:4. The tumor sizes ranged from 2.0 to 5.0 cm (mean 3.5), and the tumors exhibited a spongy appearance reminiscent of bubble wrap. Tissue samples from all of the patients exhibited a microscopic appearance characterized by cystic dilated tubules of various sizes lined by a single layered epithelium. The cells of the epithelial lining varied with respect to cuboidal, flat or squamous morphology. All cases were classified as International Society of Urological Pathology (ISUP) grade 3 and renal tumor stage pT1a. During a median follow-up period of 41 months, no patients presented with recurrent or metastatic disease. Immunohistochemistry revealed that all of the patient samples expressed AMACR, vimentin and PAX-8. The samples exhibited variable weak staining for CK7, CK8, CK19, 34bE12, CD10, CAIX, and SMA and negative immunoreactivity for TFE3 and CD34. Fluorescence in situ hybridization analysis revealed that 3p deletion and trisomy 7 and 17 were absent. In our study, pure TCRCCs appear to have a favorable prognosis. In addition, this study also provides the most convincing molecular evidence that TCRCC is a distinct disease and has poor relationship with papillary renal cell carcinoma.