**[980] Nodal Yield, Size and Distribution of Pelvic Lymph Node Metastases in Prostatic Adenocarcinoma: A Study of 72 Cases.***Jiyoon Yoon, Oleksandr Kryvenko, Sanjeev Kaul, Nilesh Patil, Nilesh Gupta. Henry Ford Hospital, Detroit, MI***Background:** Pelvic lymph node dissection (PLND) in prostate cancer generally involves removal of external iliac and obturator group (EO) of lymph nodes (LN). Several studies have shown that prostate cancer nodal metastases (MET) do not follow a pre-defined pathway of metastatic spread. The aim of our study was to determine the nodal yield, size and distribution of MET in different anatomic LN sites and study the benefit of inclusion of internal iliac (INT) LN in our PLND for intermediate to high risk group patients.**Design:** Pathology files of our hospital were searched for cases of PLND with MET from a period of Jan 2008 to May 2010. All positive cases were evaluated for anatomic sites of MET, number of LNs, size of largest LN, size of largest metastatic LN, and size of largest and smallest metastatic focus.**Results:** A total of 72 cases of MET were identified. All of these patients had PLND with EO and INT group. A total of 827 LN were submitted, 131 LN were positive for MET. Data on LN sites were available in 43 cases. Out of these, 22 cases had MET in EO group (51.1%) and 31 cases had MET in INT group (72%). MET in both groups were seen in 10 cases (23%). 21 cases had isolated MET to INT group (48.8%) where as 12 cases had isolated MET to EO group (27.9%). The mean LN yield was 11.49±5.83; the mean number of positive LN was 1.82±1.5; the size of largest LN was 3.51±1.54 cm; the mean size of positive LN was 0.9±0.8 cm. 43 patients had largest positive LN measuring less than 1.0 cm (59%, 43/72). The mean size of metastatic focus in these LN was 0.49 (range 0.05 – 0.6 cm).

Remainder of the adipose tissue (FAT) was submitted entirely in 31 cases. 87 LN were identified in FAT. Mean additional number of LN found in FAT was 2.8±2.3. 7 cases had positive LN (22.6%); the mean size of positive LN was 0.15 cm. Submission of FAT increased LN yield up to 11.8% and positive LN detection rate up to 5.6%. Lymph node staging itself was changed in 3 cases (3/7) from N0 to N1.**Conclusions:** 1) Metastasis from prostate carcinoma is frequently (59%) seen in small LNs (less than 1 cm). 2) Entire adipose tissue submission substantially increases the yield of LN and provides more accurate N staging. 3) Metastasis to INT group, either in combination with EO metastases or isolated INT metastasis is frequent and warrants inclusion of this LN group in all PLND done for intermediate to high risk prostate cancer patients.

Category: Genitourinary (including renal tumors)**Monday, February 28, 2011 1:00 PM****Poster Session II # 129, Monday Afternoon**