[878] Does Extensively Cystic Renal Cell Carcinoma Belong to the Same Spectrum of Tumors as Multilocular Cystic Renal Cell Carcinoma?
D Sidhu, K Trpkov, A Oryschak, A Yilmaz. Calgary Laboratory Services and University of Calgary, Calgary, Canada
Background: Multilocular cystic renal cell carcinoma (MCRCC) is a rare variant of clear cell RCC with excellent prognosis. Current WHO diagnostic criteria for MCRCC are restricted to tumors with no more than microscopic foci of clear cells in the septa. It is uncertain whether extensively cystic renal cell carcinomas (ECRCC) containing only microscopic nodules of clear cells have the same excellent outcome.
Design: We retrieved all cystic clear cell RCC from our institutional database containing 478 clear cell RCC, resected between 01/2000 and 08/2008. First, we excluded all cases with any solid component described grossly in the report. On microscopic review, the diagnosis of MCRCC was established only when WHO criteria were met. We also studied the ECRCC which had the same gross appearance as MCRCC, but on microscopy showed expansile or solid tumor foci which did not exceed x 4 field (i.e. 5 mm). We compared the clinical and the histopathological features and the follow-up in both tumor groups.
Results: We identified 24 tumors (5% of all clear cell RCC): 13 MCRCC (2.7%) and 11 ECRCC (2.3%). All tumors had similar gross features. On histology, both MCRCC and ECRCC demonstrated mutilocular cysts that were at least partially lined by clear cells containing low nuclear grade (grade 1 or focally grade 2). ECRCC in addition showed foci of clear cells forming expansile sheets or nodules. Worrisome histologic features, such as mitoses, necrosis, perinephric/hilar fat or lymphovascular invasion and sarcomatoid change were not seen in any tumor of both groups. Patient follow-up was available in 10 (77%) patients with MCRCC and 9 (82%) patients with ECRCC. All patients were alive with no evidence of disease after a mean follow-up of 29 months (range 6 to 88). The features are summarized in the table.
| Variables | MCRCC (n=13) | ECRCC (n=11) |
|---|
| Male/Female | 6/7 | 6/5 | | Age (years, mean) | 57 | 52 | | Procedure: | | | | Partial nephrectomy | 7 (54%) | 3 (27%) | | Radical nephrectomy | 6 (46%) | 8 (73%) | | Tumor size (cm, mean) | 3 | 3.9 | | Nuclear grade: | | | | Grade 1 | 19 (69%) | 6 (55%) | | Grade 2 (focal) | 4 (31%) | 5 (45%) | | Calcification | 5 (38%) | 2 (18%) | | Mean follow-up in months (range) | 37 (21-88) | 21 (6-40) | | Disease progression | None | None |
Conclusions: Strictly defined ECRCC represent a small subgroup of clear cell RCC. ECRCC and MCRCC belong to the spectrum of RCC with low malignant potential. ECRCC had an excellent prognosis in this series with relatively short follow-up. However, larger series with longer follow-up are required to establish their prognosis.
Category: Genitourinary (including renal tumors)
Wednesday, March 11, 2009 1:00 PM
Poster Session VI # 127, Wednesday Afternoon
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