Histologic and histochemical characterization of seminal vesicle intraluminal secretions: Particular emphasis on their crystalloid morphology

Context. - We have observed intraluminal crystalloid morphology in seminal vesicles that is superficially similar to that seen in prostate neoplasia, but found little information on such morphology in the literature. Design. - Two hundred fifty-three prostate specimens (163 needle biopsies, 75 radical prostatectomies with prostate carcinoma, 11 prostates from autopsy, and 4 cystoprostatectomies without prostate carcinoma) were examined for seminal vesicle secretions, which were categorized as (a) dense platelike inspissated, (b) fluidlike, (c) crystalloid morphology, and (d) absent. Histochemical stains (periodic acid-Schiff with and without diastase, Alcian blue at pH 2.5, and mucicarmine) were performed to characterize the nature of secretions. Results. - Proteinaceous secretions were identified in 82% of seminal vesicles examined. Of these, 61% had predominantly dense, platelike, inspissated secretions, 15% had predominantly fluidlike secretions, and 24% had predominantly crystalloid morphology. Although in some cases the crystalloid morphology resembled that of prostatic intraluminal crystalloids, the seminal vesicle crystalloids differed in that they were invariably multiple, had curved edges, and had varied forms (elliptical, cylindrical, rodlike, and rectangular). Seventy-one percent of seminal vesicle crystalloids were associated with dense, platelike, inspissated secretions and appeared to be created by fracturing within platelike secretions. There was no relationship between seminal vesicle crystalloid morphology and associated malignancy in the prostate gland, as it was seen in 24% of cases with prostate carcinoma and 25% of cases without prostate carcinoma (P = 1.0000). Fluidlike secretions were positive for Alcian blue (pH 2.5) and mucicarmine, whereas dense platelike secretions and crystalloid morphology were negative for Alcian blue (pH 2.5) and mucicarmine. Conclusions. - Seminal vesicle secretions are fairly common and, when fluidlike, are composed of acid mucopolysaccharides. Inspissation of secretions appears to be associated with loss of acidity, presumably resulting in dense platelike secretions and crystallization. Awareness of both the crystalloid morphology in seminal vesicle tissue and the distinguishing features from prostatic crystalloids may be important while interpreting prostate needle biopsies in which seminal vesicle epithelium may be confused for prostate carcinoma because of a small acinar morphology with accompanying cytologic atypia and crystalloid morphology.