IMAGING

Focal prostatic atrophy: mimicry of prostatic cancer on TRUS and 3D-MRSI studies
Prando A, Billis A
Department of Radiology, Hospital Vera Cruz and Department of Anatomic Pathology, School of Medicine, Campinas, SP, Brazil
Abdom Imaging. 2008 (published online 4 march 2008), ISSN: 1432-0509

• Objective: It is well known that histologically focal prostatic atrophy (FPA) is one of the most frequent mimics of prostatic adenocarcinoma. The purpose of our study was to show that FPA may also simulate prostate cancer on transrectal ultrasound studies (TRUS) and on 3D-magnetic resonance spectroscopic imaging of the prostate (3D-MRSI).
• Materials and Methods: From 2004 to 2006, 625 men suspected of prostate cancer, underwent TRUS guided biopsy (n = 513, group I) or TRUS-guided biopsy directed with 3D-MRSI of the prostate (n = 142, group II). The latter group was formed only by patients with elevated PSA levels and prior negative prostate biopsies. All sites showing FPA on histopathologic analysis were correlated with findings observed on gray scale and color Doppler-TRUS studies or on 3D-MRSI of the prostate.
• Results: From a total of 513 patients biopsied and studied by gray scale and color Doppler-TRUS(Group I) , 48 patients (9.3%) presented histological diagnosis of FPA associated with sonographic abnormalities in the peripheral zone of the prostate. Thirty-two patients presented hypoechoic nodules with absent flow and 16 patients had hypoechoic nodules with increased flow. From a total of 142 patients submitted to TRUS-guided biopsy directed with 3D-MRSI (Group II), 16 (11.2%) presented histological diagnosis of FPA associated with abnormalities strongly suspicious for prostate cancer on conventional MRI and/or on 3D-MRSI. These abnormalities were: focal area of low signal intensity on T2-w image or clusters of voxels with choline + creatine/ citrate ratio above 3 SDs.
• Conclusion: Similarly to the histopathologic findings focal prostatic atrophy may mimic cancer on gray-scale and color Doppler-TRUS studies and on 3D-MRSI studies. Radiologists should be aware of this entity which together with prostatitis, represent an important cause of false-positive result on prostatic biopsy directed with endorectal MRSI (11.2%).
  
  
• Editorial Comment
  Prostatic atrophy is one of the most frequent mimics of prostatic adenocarcinoma. There are still controversies regarding the causal linkage of FPA to the prostate cancer and to other pre-neoplastic lesions. On conventional and color Doppler transrectal ultrasound and on magnetic resonance spectroscopic imaging studies (MRSI), FPA may also simulate prostate cancer. The vast majority of our cases that simulate prostate cancer were related to sub-type hyperplastic prostatic atrophy. We might speculate why FPA manifests as false-positive MRSI findings: in the hyperplastic sub-type, the number of cellular membranes are increased. This could explain the elevation of choline level without modification of the polyamine level. It has been shown that there is a positive and significant association between extent of FPA in biopsies and serum total or free PSA elevation. For this reason, pathologists should include the presence of FPA in the pathology report of a prostatic biopsy, particularly in those patients with absence of cancer. When extensive FPA is the only finding in patients with several negative prostatic biopsies, this lesion may be the source for PSA elevation.

Dr. Adilson Prando
Chief, Department of Radiology and
Diagnostic Imaging
Vera Cruz Hospital
Campinas, São Paulo, Brazil
E-mail: aprando@mpc.com.br