Login to Access Video or Poster Abstract: MP87-17
Sources of Funding: Washington University School of Medicine, Division of Urology

Introduction

Suspicious lesions on prostate MRI have been correlated to prostate cancer (PCa) on prostatectomy specimens. However, targeted biopsies of even highly suspicious prostate MRI lesions (i.e. PIRADS 4 or 5) are found to be benign in multiple reported series. One potential factor leading to this discrepancy is the presence of leukocytes, as they may be present in both a small focus of benign inflammation or present as tumor-infiltrating lymphocytes.

Methods

Reviewing patients with PIRADS 4 or 5 lesions that received MRI targeted as well as systematic biopsy from December 2014 to December 2015, we developed a study cohort for additional pathologic review. We excluded patients with a clinical history of prostatitis, prior prostate biopsy within 12 months, multiple MRI suspicious regions (MSR), and MSR < 0.25 mL. The MRI targeted biopsy specimen (MRI+) and a systematic biopsy specimen geometrically distant from the MSR (MRI-) were stained for leukocytes (CD45). Blinded to the MRI result, leukocyte density (LD) was measured manually (number per mm) and presence of PCa was noted. The groups were compared using the unpaired t test.

Results

For the overall study cohort, the mean LD for MRI+ biopsy cores was significantly higher than for MRI- biopsy cores (71.9+25.4 versus 42.1+10.6, p=0.04). Within the subset of only MRI+ biopsy cores, mean LD was not different based on the presence of PCa (71.8+28.0 versus 72.0+53.7, p=0.99). Within the subset of only MRI- biopsy cores, mean LD was not different based on the presence of PCa (39.3+11.2 versus 52.2+28.3, p=0.34). An example of similar LD in two MRI+ biopsy cores, despite PCa in one but not the other is provided.

Conclusions

The LD was significantly higher for biopsy cores from MRI suspicious areas, irrespective of the presence of PCa. The MRI appearance may be representative of leukocytes (benign inflammation of tumor infiltrating lymphocytes) rather than PCa.

Funding

Washington University School of Medicine, Division of Urology