Do clinically insignificant tumors of the prostate exist?

The discrepancy between minimal disease on biopsy and disease found in the subsequent prostatectomy specimen, in terms of the size and grade of tumor, extracapsular extension or positive margins, led several authors to dispute the existence of clinically insignificant impalpable tumors of the prostate. However, considering that prostate-specific antigen (PSA) is an indicator of prostate malignancy and since many impalpable prostatic carcinomas (PCs) are detected by a combination of PSA, transurethral ultrasound and needle biopsy (T1c), in the era of PSA screening, it is expected that most of the impalpable tumors found incidentally at transurethral resection of the prostate (stage T1a/b), could be clinically insignificant.

The aim of this study was to identify the characteristics of latent, impalpable PCs and to analyze the incidence of clinically insignificant PCs among hypothetical stage T1 prostate cancers in tumors found incidentally at postmortem examination.

We examined 40 cases of impalpable PCs found in 212 prostate autopsy specimens of men between 30 and 98 years of age who died of diseases other than carcinoma of the prostate and related conditions.

Most of T1 histological PCs (57.5%) had a Gleason score between 2 and 4, while 30% had Gleason score between 5 and 6. Only 5 (12.5%) had a Gleason score above 7. Twenty-nine of 40 stage T1 histological cancers (67.5%) had volume of <1 cm(3). The highest volume tumors were those of intermediate and high grade (Gleason sums 5-8). Among tumors with volumes of <1 cm(3), 96.55% were confined within the prostatic capsule.

The majority of impalpable PCs were low-volume, well-differentiated tumors corresponding to clinically insignificant neoplasms. Similar characteristics could be attributed to most of the impalpable carcinomas detected after prostatectomy in clinical practice.