Correspondence *Department of Urology, First Floor, Thomas Guy's House, Guy's Hospital, London SE1 9RT, UK

Email shamim.khan@gstt.nhs.uk

The case

A 43-year-old man with no remarkable medical history presented with two years' recurrent hematospermia and left testicular pain. He also reported mild erectile dysfunction (International Index of Erectile Function score 18 out of 25). He did not have a history of urinary tract infections or sexually transmitted diseases. Apart from a tender left epididymis, external genitalia were normal on examination. On digital rectal examination his prostate was found to be small in size and benign in consistency. Seminal vesicles were not palpable.

Transrectal ultrasonography (TRUS) showed a localized tumor of the left seminal vesicle. Routine blood tests, including PSA, testosterone and prolactin levels, were normal. Transabdominal ultrasonography, intravenous urogram and cystoscopy performed for coincidental microscopic hematuria showed no abnormality. MRI confirmed a 3 2 cm low-signal, soft tissue mass within the left seminal vesicle, extending to the level of the ejaculatory duct with some dilatation of the left vas deferens and the proximal part of the seminal vesicle (Figure 1). The mass was well circumscribed; the prostate and bladder appeared normal. There was no evidence of pelvic lymphadenopathy. TRUS-guided needle biopsy proved inconclusive.

Figure 1 MRI scan showing a 3 2 cm low-signal, soft tissue mass within the left seminal vesicle

 

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The patient was counseled for laparoscopic excision of the left seminal vesicle. He was placed in the Trendlenberg position, and a camera port was inserted through a small peri-umblical incision using the Hassan technique. Three 5 mm ports and one 10 mm port were inserted under direct vision as shown (Figure 2). After preliminary inspection of the intra-abdominal viscera, the left vas deferens was identified and dissected down to the seminal vesicle, which was fully mobilized. Particular care was taken at the apex of the seminal vesicle to minimize damage to the pelvic plexus. The left seminal vesicle, along with the tumor and adjoining vas deferens, was excised and clear margins were ensured by frozen section. Total operative time was 75 minutes with 200 ml of blood loss. The patient's recovery was uncomplicated and he was discharged on the second postoperative day.

Figure 2 Port configuration for laparoscopic excision of the left seminal vesicle

 

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On gross examination the specimen consisted of a distorted and bulbous seminal vesicle with an intact and smooth external surface (Figure 3). On serial sectioning of the specimen, the seminal vesicle was expanded by a partly solid and partly cystic white mass that measured 55 30 25 mm.

Figure 3 Distorted and bulbous seminal vesicle with an intact and smooth external surface

 

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Histologic examination demonstrated a biphasic tumor that arose from the internal aspect of the wall of the seminal vesicle, filling the expanded lumen. The wall of the seminal vesicle was distorted and thinned by the mass but remained intact.

Microscopic examination of the tumor showed stromal proliferation with areas of hypocellularity interspersed with moderately hypercellular areas. The background parenchyma was composed of generally loose connective tissue, although there were foci of hyalinization associated with the less cellular areas.

The stromal proliferation formed broad papillae, which were separated by narrow cleft-like spaces, producing a frond-like or leaf-like architecture. The clefts were lined predominantly by a single layer of cuboidal to low columnar epithelial cells (Figure 4). Focally, however, there was stratification of the epithelial cells associated with foci of apical 'snouting' (Figure 5) and decapitation secretions. The epithelial cells showed no atypical features. Within the broad stromal papillae there were invaginations of the surface epithelium, and occasional aggregates of small, tubular, gland-like structures lined by epithelial cells with similar morphological characteristics to those lining the clefts (Figure 6).

Figure 4 Hematoxylin and eosin-stained low-power photomicrograph of the tumor

The wall of the seminal vesicle (the external surface of which is inked) is distended by a fibrous stromal mass, which forms broad papillae, separated by cleft-like spaces, and lined by a thin layer of cuboidal to low columnar epithelium.

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Figure 5 Photomicrograph showing lining epithelium with focal apocrine snouting

 

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Figure 6 Photomicrograph showing artefactual tubular invaginations into the stroma, lined by the same epithelium

 

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The stromal cells were generally bland, and varied in shape from spindle to plump and round (Figure 7). However, a proportion of these cells showed mild nuclear enlargement and very occasional multinucleate forms. The nuclei were predominantly vesicular, and nucleoli were not prominent. There were very occasional mitotic figures (up to 2 in 50 per high power field examined) (Figure 8), none of which was atypical (Figure 9).

Figure 7 Photomicrograph showing hypocellular, hyalinised stroma

The stromal cells are spindled with bland nuclei.

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Figure 8 Photomicrograph showing very infrequent mitotic figures within the stroma

 

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Figure 9 High-power photomicrograph of lining epithelium, showing focal, mild stratification of cells and very occasional mitotic figures

 

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There was no necrosis within any of the extensive blocks sampled. No residual native seminal vesicle epithelium was identified within the tumor. The glandular tissue adjacent to the seminal vesicle, including the glandular components and the vas deferens, were unremarkable. The morphologic appearance was that of a low-grade phyllodes tumor of the seminal vesicle. Immunohistochemistry confirmed cytoplasmic reactivity for carcinoembryonic antigen and absence of staining for PSA and prostatic acid phosphatase.

Discussion of diagnosis

Primary seminal vesicle tumors are very rare; less than 100 cases have been reported in the English literature to date. Patients usually present with lower urinary tract symptoms or hematospermia. As diagnosis is often delayed, dissemination at presentation is not uncommon. Seminal vesicles are, however, usually involved secondarily to tumors from adjacent organs, particularly the prostate. Tumors of the seminal vesicles can be classified into three groups: primary adenocarinoma; metastases and contiguous spread; soft tissue and other tumors.

Among the primary neoplasms, adenocarcinoma is the most common primary malignant tumor of the seminal vesicles. Mean age at presentation is 62 years (range 17–90 years). The majority of patients present with symptoms of urinary outflow obstruction or hematospermia.^{1, 2}

As secondary tumors are more common than primary tumors, the precise pathologic diagnosis of primary adenocarcinoma of the seminal vesicle can only be made if the tumor is located within the seminal vesicle and there is no concomitant tumor in any of the adjacent organs including the prostate, bladder or colon. Histologically, the tumor should have the architectural features of adenocarcinoma, with a papillary or sheet-like growth pattern, mucinous differentiation and carcinoma in situ in the adjacent epithelium lining the seminal vesicle. Immunohistochemistry should demonstrate cytoplasmic reactivity for carcinoembryonic antigen but absence of staining for PSA and prostatic acid phosphatase. The main reason for setting these criteria is that, in cases of locally advanced and high-grade tumors, it may be exceedingly difficult to determine the precise site of origin of the tumor, and tumor cells may appear hobnail, polygonal or columnar with clear cytoplasm.³ Slayter et al. proposed stratification of the primary adenocarcinoma of the seminal vesicles into three groups: in situ, invasive without desmoplasia and invasive with desmoplasia.⁴

Secondary involvement of the seminal vesicles is usually caused by contiguous spread of tumors from the adjacent organs, and occasionally by metastatic spread. The tumors likely to spread to the seminal vesicles originate from the prostate, bladder and rectum (in decreasing order of frequency). Spread of prostatic adenocarcinoma to the seminal vesicle is the most frequent occurrence. Even in cases of presumed localized adenocarcinoma of the prostate, seminal vesicle involvement is found in up to 12% of radical prostatectomy specimens.

There are three patterns of spread of prostatic adenocarcinoma to the seminal vesicle; direct spread along the ejaculatory duct complex into the seminal vesicles, prostatic capsular perforation followed by extension into the peri-prostatic tissues and the seminal vesicles, and spread by isolated deposits.⁵

Bladder tumors can spread to the seminal vesicles if locally advanced, particularly those that arise from the trigone or base of the bladder. Rarely, the seminal vesicles may be involved by the mucosal spread of the carcinoma in situ of the bladder; the usual route of such a spread is via the prostatic urethra, to the prostatic and ejaculatory ducts and subsequently to the seminal vesicles, or by intra-epithelial replacement or pagetoid spread along the basement membrane.⁶

Adenocarcinoma of the rectum can, in a similar way, spread to the seminal vesicles in locally advanced cases. Metastases to the seminal vesicles are rare but a case of metastatic seminoma has been reported in the literature. Besides the above groups of tumors, a variety of soft tissue tumors, consisting of pure stromal elements such as leiomyomas and fibromas, can arise from the seminal vesicles. There is a unique group of tumors, called 'mixed tumors', which can arise from the seminal vesicles; as the name implies, these are composed of a mixture of epithelial and stromal elements. Mixed tumors are extremely rare; only 15 cases of such tumors have been reported in the English literature, variously described as cystadenoma, cystomyoma, low-grade phyllodes tumor, benign mesenchymoma, adenomyosis, and mesonephric hamartoma.

According to the WHO criteria, to qualify for the diagnosis of a mixed seminal vesical tumor the neoplasm must originate from the seminal vesicle. There should be no normal seminal vesicle within the tumor. The tumors should not invade the prostate and immunohistochemistry must be negative for prostate tumor markers (PSA and prostate acid phosphatase) and carcinoembryonic antigen. As cystadenoma did not fulfil the criteria of mixed tumors it was excluded from the WHO list of mixed tumors published in 2004.⁷

The term 'phyllodes tumor' has been applied to a group of tumors with a foliated structure, which are composed of spindle cell stroma and benign epithelial elements. The most common site of origin of these tumors is the breast, followed by the prostate and, rarely, the seminal vesicles. Tumors are categorized either as fibroadenoma, low-grade phyllodes tumor or high-grade phyllodes tumor (also called cystosarcoma phyllodes) according to the density and cytologic features of the stromal component. The presence of infiltrating margins, stromal atypia, increased number of mitotic figures and overgrowth of glands in the stroma are features indicative of malignancy.⁸

Fain et al. have categorized mixed tumors of the seminal vesicles into fibroadenomas, low-grade phyllodes tumor and high-grade phyllode tumors based on cellularity, presence or absence of atypia and the degree of mitotic activity. They proposed that mixed tumors should be categorized as fibroadenomas if the stroma is hypercellular without any atypia or mitosis. Lesions that show hypercellular stroma with atypia but only few mitoses may be regarded as low-grade phyllodes tumor. On the contrary, lesions that show atypical hypercellular stroma and frequent mitosis (1–5 per 10 high-power fields) should be categorized as high-grade phyllodes tumor or cystosarcoma phyllodes. Only two cases of cystosarcoma phyllodes of the seminal vesicles have been reported in the literature.^{9, 10}

Treatment and management

We performed laparoscopic excision of the tumor-bearing seminal vesicle, using the same approach as laparoscopic radical prostatectomy. Pathologically, the margins were reported clear. There is no evidence of local recurrence or distant metastases 1 year post-surgery. Only long-term follow-up of the patient will determine the ultimate outcome.

Both of the previously reported patients with cystosarcoma phyllodes underwent open surgery. The patient reported by Fain et al. had a fairly large tumor that measured 8.5 cm, which was adherent to the posterior bladder and anterior rectal wall. The patient was treated with radical surgery, which entailed cystoprostatosemino-vesiculectomy, bilateral pelvic lymphadenectomy, lower anterior resection of the sigmoid colon and ileal conduit urinary diversion. He developed pulmonary metastasis 4 years later, which was treated by excision and postoperative chemotherapy. In spite of positive rectal margin, there was no mention of local recurrence. The patient was alive after 6 months' follow-up, when chemotherapy for metastatic disease was complete.

In the second case, Abe et al. performed open surgery to remove the tumor and the ipsilateral seminal vesicle. Their patient developed pulmonary metastases in the following 7 months and died after 11 months. These two cases highlight the unpredictable behaviour of the tumor, but the exact prognosis and histogenesis of phyllodes tumors of the seminal vesicle can only be determined by the accumulation of data from additional reported cases.

The only case of low-grade phyllodes tumor of the seminal vesicle was reported by Son et al. in 2004.¹¹ The patient, aged 39 years, presented with urinary retention and lower abdominal discomfort. CT showed a very large cystic mass behind the bladder. The patient underwent open surgery to remove the mass and the left seminal vesicle. He was reported to be alive with no evidence of local recurrence or distant metastases 1 year after surgery.

Conclusions

Investigations in most cases of hematospermia are inconclusive but can, on rare occasions, be associated with serious pathology of the urogenital tract. Minimally invasive surgery is steadily becoming the standard procedure for the management of prostate and bladder tumors. If expertise is available, therefore, any suitable patients with operable seminal vesicle lesions should be offered the option of minimally invasive surgery for its obvious benefits of minimal blood loss, short hospital stay and quick return to normal activity.

References

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Subject areas under which this article appears: Urologic oncology (nonprostatic)