[843] Kidney Biopsy for Tumors: Pathologic Interpretation and Clinical Significance.

Julie M Huss, Steven Raman, Jiaoti Huang. UCLA David Geffen School of Medicine, Los Angeles, CA

Background: Kidney tumors have traditionally been treated with nephorectomy. The current trend is to observe benign tumors while ablating those that are small. In these situations, a kidney biopsy is critical to document the tumor type for management and prognosis, but diagnosis can be challenging as different types of renal tumor have overlapping features and the samples are usually smaller than what most pathologists are used to working with. This study was performed to summarize our experience in interpreting such biopsies.
Design: From 2002 to 2010, 138 renal mass biopsies were performed in our institution. Patient demographics, final pathology diagnosis, immunohistochemical studies used and if available, subsequent nephrectomy specimens were analyzed.
Results: 1. The patients consisted of 102 men and 36 wemen, between 29-88 years of age. Of them, 93 cases (67%) were malignant, 30 (22%) were benign including 16 oncocytomas and 4 angiomyolipomas, 9 (7%) were inconclusive and 6 (4%) were non-diagnostic.
2. Immunohistochemistry was performed in 92 (67%) cases.
3. Of the 93 malignancies, 85 (91%) were renal cell carcinomas (RCC). The remaining cases were metastatic tumors, lymphomas, and poorly differentiated carcinoma NOS.
4. RCCs consisted of 60 cases (71%) of clear cell type, 10 cases (12%) of papillary type (8 type I and 2 type II), 2 cases (1.4%) each of chromophobe and the newly described oncocytic papillary type, 1 case (0.7%) each of multilocular cystic RCC and collecting duct carcinoma. 9 cases (6.5%) were unclassified.
5. The majority of the patients received ablation at the time of biopsy with biopsy tissue the only material documenting the tumor type.
6. 16 cases diagnosed as malignant had subsequent nephrectomy, of which 15 cases (94.4%) had identical diagnosis as biopsy. 1 case of RCC was changed from clear cell type on biopsy to papillary type II on nephorectomy.
7. 2 cases with inclnclusive biopsy diagnosis also had sebsequent nephorectomy and both showed benign lesions.
Conclusions: 1. Renal biopsy for mass lesions is increasingly used, particularly for small lesions that can be safely ablated and for lesions that are possibly benign by radiology.
2. Using the same criteria for nephorectomy specimens, a definitive diagnosis can be rendered in the majority of the renal tumor biopsies with remarkable accuracy.
3. Immunohistochemistry is a valuable tool in helping the diagnosis and subclassification of renal tumors.
4. Used properly, renal biopsy is an important modality to arrive at a definitive tissue diagnosis without subjecting patients to major surgery.
Category: Genitourinary (including renal tumors)

Monday, February 28, 2011 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 102, Monday Morning

 

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