Purpose: Types 1 and 2 by Delahunt of papillary renal cell carcinoma (PRCC) are traditionally differentiated. An oncocytic variant of PRCC (O-PRCC) has recently been described. We compare clinical data of O-PRCC with other subtypes of PRCC such as the main tumour size, necrotic changes, presence of pseudocapsula and real extrarenal growth in retrospective study.
Methods: From 1/1992 to 10/2009, 1,398 patients with 1,436 renal tumours were surgically treated in our institution. PRCCs were described in 109 (7.6%). Among PRCC, O-PRCCs were in 12 (11%), PRCC type 1 in 86 (78.9%), PRCC type 2 in 8 (7.3%) and others in 3 (2.8%) cases.
Results: The patient's mean age with O-PRCC (M:F ratio = 2:1) was 67.5 +/- 10.9 versus 63.5 +/- 14.1 in type 1 and 57.9 +/- 5.7 in type 2, the mean tumour size was 35 +/- 12 mm versus 47 +/- 22 and 37 +/- 17, respectively. The follow-up of O-PRCC is 35.3 +/- 12.3 months and all cases are without recurrence. We did not find any pseudocapsula in O-PRCC but it was a major sign of PRCC type 1 (32.6%). Huge microscopic necrotic changes were described in 33.3% of O-PRCC, in 33.7% of PRCC type 1 and 62.5% of PRCC type 2. Extrarenal growth was found only in 16.7% O-PRCC versus 40.7% in PRCC type I.
Conclusions: None of the O-PRCC had pseudocapsula and none had massive necroses in comparison of O-PRCC with PRCC types I and II. Extrarenal growth in O-PRCC is relatively rare. The malignant potential of O-PRCC is low.