EAU 2018: Does Renal Biopsy Make Sense in View of Tumor Heterogeneity?

Copenhagen, Denmark (UroToday.com)  Dr. Holger Moch, a pathologist from University Hospital Zurich presented a discussion regarding the role of renal biopsy from the pathologist’s perspective. Tumor heterogeneity, in terms of morphology, grade and molecular characteristics, is well recognized in renal tumors, including small renal masses. Dr. Moch started by highlighting that the ASCO guidelines for small renal masses1 state that partial nephrectomy is the standard treatment for small renal masses, and that all patients with small renal masses should be considered for renal tumor biopsy when the results may alter management. Small renal masses are a heterogeneous group of tumors that include benign, indolent, and aggressive tumors. Currently MRI, CT and ultrasound imaging cannot make an absolute diagnosis of cancer, whether indolent or aggressive. As quoted in the ASCO guideline, the overall diagnostic rate of renal mass biopsy is 92%, sensitivity is 99.7% and specificity is 93.2%. Clinicians should have and understand how tumor heterogeneity could impact renal mass biopsy and a treatment plan for a given patient. 

Dr. Moch notes that the pathologic histologic spectrum of entities has expanded greatly over the last several years, including eight different histologic subtypes for renal epithelial neoplasms with low malignant behavior, and seven subtypes for renal cell carcinomas with aggressive behavior. Furthermore, there have been changes to the classification scheme since the WHO 2016 meeting. For example, the definition of adenoma in 2004 was a tumor with papillary or tubular architecture of low nuclear grade and 5 mm in diameter or smaller. The 2016 WHO update states that papillary adenomas are unencapsulated tumors with papillary or tubular architecture of low ISUP/WHO grade and 15 mm in diameter or smaller. The diagnosis of papillary adenoma on needle biopsy should be made with extreme caution as visualization of any capsule and grade heterogeneity issues may not be appreciated.

The accuracy of tumor grade is much more variable than histologic subtype. The AUA guideline for renal mass and localized renal cancer suggests that for patients with a solid renal mass who elect renal mass biopsy, multiple core biopsies are preferred over fine needle aspiration1. When assigned, histologic determination of RCC subtype is highly accurate, but accuracy for tumor grade is variable. Despite the variability in accuracy of tumor grade on renal mass biopsy, multiple studies have demonstrated that molecular subtypes of clear cell RCC are highly prognostic. 

Dr. Moch concluded with several take home points:

  1. Review of renal mass biopsy findings at multidisciplinary patient conferences and/or tumor boards provides an excellent opportunity for pathologist interaction in this regard
  2. At the present time, renal mass biopsy is used principally to provide histopathologic information
  3. In the future, genomic information from renal mass biopsy may provide prognostic information that could further change treatment approaches


Presented by: Holger Moch, MD University and University Hospital, Zurich, Switzerland

References:

1. Finelli A, Ismaila N, Durack J, et al. Management of Small Renal Masses: American Society of Clinical Oncology Practice Guideline. J Clin Oncol 2017 35;(6):668-680.
2. Campbell S, Uzzo RG, Allaf ME, et al. Renal mass and localized renal cancer: AUA Guideline. J Urol 2017;198(3):520-529.

Written by: Zachary Klaassen, MD, Urologic Oncology Fellow, University of Toronto, Princess Margaret Cancer Centre, twitter: @zklaassen_md at the 2018 European Association of Urology Meeting EAU18, 16-20 March, 2018 Copenhagen, Denmark


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