Normal tissue from seminal vesicle, ejaculatory duct, Cowper's glands, and paraganglia can be found incidentally in prostatic resection specimens and lead to diagnostic errors.^{[150,169,178,184,186]} This is particularly true for the seminal vesicle because of its complex papillary arrangement and sometimes striking nuclear aberrations (Fig. 18.7). A clue to the nature of this epithelium is the presence of abundant lipofuscin granules in the cytoplasm.^[170] It should be noted, however, that a similar pigment can be occasionally found in benign and malignant prostatic epithelium,^[135] and that the distal seminal vesicle epithelium may show some immunoreactivity for PSA. Another clue is provided by the immunoreactivity of the seminal vesicle–ejaculatory duct epithelium for MUC6.^[171]