Final Diagnosis -- Renal cell carcinoma with features of clear cell papillary subtype

FINAL DIAGNOSIS

RENAL CELL CARCINOMA WITH FEATURES OF CLEAR CELL PAPILLARY SUBTYPE.

DISCUSSION

This distinctive subtype of renal neoplasm was first described by Tickoo et al in patients with end stage renal disease and designated as "clear-cell papillary renal cell carcinoma." Gobbo et al have later described these tumors in patients without evidence of impaired renal function. These tumors are usually unicentric, unilateral and small in size. Grossly these tumors are well circumscribed and usually encapsulated. Microscopically, the tumor cells have clear cytoplasm and low grade nuclei and have papillary, cystic and tubuloacinar architecture. The available literature with clinical follow up information suggest that these tumors behave in indolent fashion.

These neoplasms are difficult to distinguish from papillary renal cell carcinomas with clear cell changes based on morphologic features alone. However these two entities have different immunohistochemical and cytogenetic profiles. Papillary renal cell carcinomas express AMACR and show gains of chromosome 7 and 17, whereas these neoplasms are negative for AMACR and donot show gains of chromosome 7 and 17. Clear cell renal cell carcinoma with areas of pseudopapillary architecture can also cause diagnostic confusion. The clear cell renal cell carcinomas are negative for CK7 and frequently show 3p deletion whereas clear cell papillary renal cell carcinomas show strong immunoexpression for CK7 and lack deletion of 3p. Another differential diagnosis for a papillary tumor lined by clear cells can be Xp.11.2 translocation renal cell carcinoma. The tumor cells of Xp11.2 translocation carcinomas characteristically show positive nuclear immunoreactivity for TFE3 unlike clear-cell papillary renal cell carcinoma.

REFERENCES

SK Tickoo, MN dePeralta-Venturina, LR Harik, et al, Spectrum of epithelial neoplasms in end-stage renal disease: an experience from 66 tumor-bearing kidneys with emphasis on histologic patterns distinct from those in sporadic adult renal neoplasia. Am J Surg Pathol. 2006;30:141-153.

S Gobbo, JN Eble, G Martignoni, et al, Clear cell papillary renal cell carcinoma: a distinct histopathological and molecular genetic entity. Am J Surg Pathol. 2008;32:1239-1245.

Contributed by Shveta Hooda, MD and Anil V Parwani, MD, PhD