Collagenous micronodules in prostate cancer. A specific but infrequent diagnostic finding

Collagenous micronodules (CMs) are microscopic stromal fibrillar aggregates of uncertain histogenesis that arise in association with prostatic adenocarcinoma. We studied a large series of biopsies and matched radical prostatectomies to determine the frequency, specificity, and predictive value of CMs.

Retrospective study of 308 needle biopsies and matched radical prostatectomies with prostate cancer.

Consecutive series of men with prostatic adenocarcinoma undergoing needle biopsy of the prostate and subsequent radical prostatectomy at a large tertiary-care academic medical center.

Incidence and extent of CMs, and correlation of CMs with multiple prognostic factors.

Collagenous micronodules were identified in 0.6% of needle biopsies and 12.7% of prostatectomies, with a median of 2.0 high-power microscopic (x 40) fields of CMs per positive prostatectomy; most cases were identified in association with mucin-producing glands. The number of fields of CMs was not related to clinical or pathologic stage, serum prostate specific antigen concentration, prostatic weight, volume of cancer, Gleason score, percent of poorly differentiated cancer, nuclear grade, or DNA ploidy content. There were no CMs in benign prostatic glands, benign prostatic hyperplasia, or prostatic intraepithelial neoplasia in any specimen. Histochemical and ultrastructural studies showed that CMs are composed chiefly of collagen; in one case, flocculent laminated calcospherites were present.

Collagenous micronodules are a specific but infrequent diagnostic clue in prostatic adenocarcinoma, particularly in those with prominent mucin production, but are not associated with factors predictive of progression.