What is RCC, and what are its histologic subtypes?
RCC is the most common primary malignant tumor of the kidney, accounting for >90% of renal malignancies, most often arising in patients in the seventh through eighth decades of life, and occurring two to three times more commonly in men than in women. With the extensive use of cross-sectional imaging in clinical practice, 60% to 70% of renal neoplasms are discovered incidentally during imaging for other causes. The Fuhrman nuclear grading system is typically used to histopathologically grade RCC, where grade I carries the best prognosis and grade IV carries the worst prognosis. Treatment of RCC may involve total nephrectomy, partial nephrectomy, cryoablation, or radiofrequency ablation, and chemotherapy is administered when metastatic disease is present. Nephron sparing surgery is the treatment of choice, whenever feasible, with thermal ablation usually reserved for patients who are poor surgical candidates.
Clear cell (conventional) RCC is the most common histologic subtype, accounting for 75% of cases, contains microscopic lipid, and is associated with the second worst prognosis.
Papillary RCC accounts for 10% of cases and is generally associated with a good prognosis. Type I (basophilic) papillary RCC is more indolent, whereas type II (eosinophilic) papillary RCC is more aggressive.
Chromophobe RCC accounts for 5% of cases and is associated with the best prognosis.
Collecting duct RCC (including the renal medullary subtype) accounts for 1% of cases, is typically highly aggressive, and is associated with the worst prognosis. The renal medullary subtype is most commonly seen in young patients with sickle cell trait.
The remaining 4% of RCC are unclassified.