Discussion
BGP in WT is referred in literature as Botryoid WT. We preferred the term Botryoid Growth Pattern to avoid any confusion between gross and microscopic patterns. BGP in BWT is extremely rare. The two patterns revealing the disease (abdominal mass and gross hematuria) were frequently observed in most unilateral BGP cases in literature4-10. Because the tumor was prone to extend into the proximal ureter, hydronephrosis was often present on diagnostic images. The dilation of the three calices may be an important radiologic feature to preoperatively detect the presence of BGP.
The predisposing syndromes associated with BGP were scarcely described. Among 77 patients (8 BWT), Vujanić et al reported only one patient with Denys-Drash syndrome2. In our cases, two children had a WT1 mutation, in relation with the bilateral disease.
The surgical management of BWT represents a challenge, and discovering a BGP makes the conservative surgery more complicated, particularly to remove the whole tumor and the botryoid mass in the pelvis, without any rupture. In addition, the size of WT was high, rendering the decision of NSS even more difficult. However, the WT with BGP was located to the lower pole of the right kidney in all cases and NSS was feasible, with opening of the renal pelvis and the calyx in order to extract the tumor. No tumor breach was observed, and 30 to 50% of renal parenchyma was preserved. The tumor and the BGP were removed en bloc and entirely in the three cases.
The histological type of WT was stromal or mixed type in our patients and in both kidneys for each patient, but the BGP itself was an ILNR every time. In literature, nephrogenic rests were found in 50% of tumors with BGP2. Yanai et al suggested that the BGP originated from the ILNR of the pelvis6.
BGP itself did not change the stage or the prognosis of the disease. Vujanić et al concluded that the intra pelvic botryoid growth should not be a reason for upstaging a tumor2. Even when tumor extends into the ureter and reaches the bladder without infiltrating the wall, it should still be regarded as stage 1 if completely excised.
The outcome was excellent in patients 1 and 2. They have a moderate renal insufficiency, with their native kidneys. We only have 9 months follow-up for patient 3, who has already a renal insufficiency along with a WT1 mutation.