Login to Access Video or Poster Abstract: MP67-16
Sources of Funding: None

Introduction

The optimal surgical margin for small renal masses is contested. Recognition of a circumferential, intact radiographic pseudocapsule using MRI is a novel approach to determine if minimal parenchymal resection can be performed while to maximize nephron sparing and to achieve negative margins. Our goal was to characterize the parenchymal-tumor interface (PTI) using preoperative MRI imaging and to correlate with histopathology. _x000D_

Methods

We identified 42 of 200 patients who underwent preoperative MRI imaging and subsequent robotic partial nephrectomy. We characterized each RCC by defining the MRI sequence that best illustrated the PTI. We then commented on the capsule, its intactness, shape, and abutting of the collecting system. Finally, positive surgical margin status was correlated to the MRI findings.

Results

14 tumors were primarily cystic, while 28 were primarily solid. Tumors that were primarily cystic most clearly showed a traditional hypointense band on T2 Haste/SSFSE (13/14). However, we found that the patients with solid masses exhibited a pseudocapsule best on T2 Postcontrast scans (15/28) (Fig. 1). A capsule of some sort was noted in all cases. The outline was circumferential around the mass in 39/42 cases and a smooth parenchymal/tumor interface was seen in 36/42 cases. Of three cases with preoperative MRI infiltration, 2 resulted in positive surgical margins. The average pseudocapsule score was a 1.92, indicating that the pseudocapsule was focally infiltrated, but not fully penetrated._x000D_

Conclusions

The findings of this study suggests that both T2 Haste/SSFSE and T2 Postcontrast scans are efficacious in characterizing the PTI, but the latter is particularly helpful for solid masses. Other histological findings display that most parenchymal/tumor interfaces are smooth, circumferential, and often abutting the collecting system. The histological findings suggest that most tumors are not fully infiltrating the surrounding parenchyma, and the vast majority demonstrated negative margins when analyzed. _x000D_ These findings suggest that preoperative MRI is useful in characterizing the PTI in patients with RCC, and can provide surgeons with useful information to guide surgical technique._x000D_

Funding

None