Synchronous seminal vesicle metastasis from rectosigmoid adenocarcinoma: A case report

Abstract

BACKGROUND

Seminal vesicle metastasis from colorectal cancer (CRC) is extremely rare and poses diagnostic and therapeutic challenges. Limited cases have been reported, and its clinical characteristics remain poorly understood.

CASE SUMMARY

We report a case of synchronous seminal vesicle metastasis originating from rectosigmoid adenocarcinoma. The diagnosis was established through imaging and confirmed by histopathology. The patient underwent surgical resection followed by adjuvant chemotherapy and achieved favorable outcomes with no evidence of recurrence during a two-year follow-up period.

CONCLUSION

Seminal vesicle metastasis should be considered in atypical cases of CRC.

Key Words: Colorectal neoplasms; Seminal vesicle; Neoplasm metastasis; Rectosigmoid junction; Diagnosis; Case report

Core Tip: Seminal vesicle metastasis from colorectal cancer is extremely rare and difficult to diagnose. We report a case of synchronous metastasis from rectosigmoid adenocarcinoma confirmed by imaging and histopathology, with favorable long-term outcomes. This case highlights the importance of distinguishing distant metastasis from direct invasion and supports comprehensive treatment strategies.

INTRODUCTION

Colorectal cancer (CRC) is one of the most common malignancies worldwide, frequently metastasizing to the liver and lungs[1-3]. However, metastasis to the seminal vesicle is exceedingly rare, with very few cases reported in the literature. Due to its rarity, the clinical characteristics, diagnostic approach, and optimal management remain unclear. Here, we report a rare case of synchronous seminal vesicle metastasis from rectosigmoid adenocarcinoma and discuss its diagnostic and therapeutic implications.

CASE PRESENTATION

Chief complaints

A 66-year-old male presented with abdominal distension for more than one month, which had significantly worsened one day prior to admission.

History of present illness

The patient reported progressive abdominal distension mainly located in the periumbilical region, accompanied by acid reflux, belching, vomiting, and difficulty in defecation. He also experienced an unintentional weight loss of approximately 5 kg over the past month. Importantly, he did not present with any urinary or other urogenital symptoms suggestive of seminal vesicle involvement, including dysuria, urinary frequency, urgency, hematuria, pelvic pain, perineal discomfort, or ejaculatory dysfunction.

History of past illness

The patient had a history of hypertension for 7 years, which was well controlled with enalapril. No other significant medical history was reported.

Personal and family history

The patient denied any family history of malignant tumors. No relevant personal or genetic disease history was reported.

Physical examination

On admission, the patient’s vital signs were stable. Abdominal examination revealed a soft but distended abdomen without tenderness or rebound tenderness. Digital rectal examination showed no obvious abnormalities.

Laboratory examinations

Laboratory tests revealed an elevated carcinoembryonic antigen level of 22.40 ng/mL. Alpha-fetoprotein (4.22 ng/mL), carbohydrate antigen 125 (18.10 U/mL), and total prostate-specific antigen (0.887 ng/mL) were within normal ranges.

Imaging examinations

Enhanced abdominal computed tomography revealed features suggestive of bowel obstruction, including localized narrowing at the rectosigmoid junction, luminal stenosis, and significant irregular enhancement with diffuse thickening of the colorectal wall. Multiple enlarged pelvic lymph nodes were observed. In addition, a nodular enhancing lesion was identified posterior to the right seminal vesicle. Colonoscopy demonstrated an ulcerative circumferential mass located 12 cm from the anal verge, causing luminal narrowing and preventing further advancement of the endoscope (Figure 1).

Figure 1 Imaging and pathological findings of synchronous seminal vesicle metastasis from rectosigmoid adenocarcinoma. A: Contrast-enhanced computed tomography showing localized narrowing at the rectosigmoid junction, luminal stenosis, and irregular enhancement with diffuse thickening of the colorectal wall; B: Nodular enhancing lesion posterior to the right seminal vesicle; C: Colonoscopy showing an ulcerative circumferential mass with luminal narrowing; D: Moderately differentiated adenocarcinoma invading the subserosal layer. Scale bar: 50 μm; magnification, × 100; E: Cancer cells infiltrating the stromal and muscular layers of the seminal vesicle and forming invasive nests. Scale bar: 200 μm; magnification, × 40.

FINAL DIAGNOSIS

Adenocarcinoma of the rectosigmoid junction with synchronous seminal vesicle metastasis (pT3N2bM1, MSS).

TREATMENT

The patient underwent emergency intestinal stent placement followed by laparoscopic radical resection and right seminal vesicle resection. Postoperatively, 12 cycles of mFOLFOX6 chemotherapy were administered.

OUTCOME AND FOLLOW-UP

At the two-year postoperative follow-up, there were no signs of recurrence or metastasis to date (Figure 2).

Figure 2 Timeline of the diagnostic and therapeutic course of the patient.

DISCUSSION

CRC is one of the most common types of cancer, with metastatic sites frequently including regional lymph nodes, the liver, the lungs, and the peritoneum. For patients with resectable metastatic lesions, R0 surgery is considered to improve prognosis, particularly for liver and lung metastases; five-year survival rates after surgery can reach 36% to 58% and 60%[4], respectively. However, when CRC involves rare metastases, such as to the seminal vesicles, the clinical course and prognosis remain poorly defined because of the limited number of reported cases. Available reports suggest that patients with CRC and seminal vesicle metastasis generally have poor outcomes[1]. Although primary tumors and direct invasion account for most malignant involvement of the seminal vesicle, the seminal vesicle gland may also serve as a rare site of distant metastasis. Reports have documented cases of distant metastasis to the seminal vesicle gland from renal cell carcinoma[5], liver cancer[6], lung cancer[7], CRC[1], and thymoma[8].

Because of the extreme rarity of this metastatic pattern, the underlying mechanism remains poorly understood. Potential routes include hematogenous dissemination, lymphatic spread through the pelvic lymphatic network, and retrograde venous spread through the pelvic venous plexus[1,9-11]. In the present case, the lack of radiologic, intraoperative, and histopathological evidence of direct contiguous extension suggests that hematogenous or lymphatic dissemination represents the most plausible mechanism of metastasis.

The rarity of seminal vesicle tumors combined with the lack of specific early clinical symptoms often complicates diagnosis, leading to delays. When the disease progresses to an advanced stage, major symptoms of the urogenital system, such as difficulty urinating, frequent urination, hematuria, and bladder outlet obstruction, gradually become apparent[12]. Imaging therefore plays an essential role in the detection and evaluation of these lesions. Conventional imaging modalities, including computed tomography and magnetic resonance imaging, are valuable for identifying pelvic lesions and assessing tumor relationships with surrounding structures. In addition, 18F-fluorodeoxyglucose positron emission tomography (PET)/computed tomography (CT) has demonstrated particular value in detecting unusual metastatic sites and evaluating systemic tumor spread[9]. However, PET/CT was not performed in the present case because of patient-related economic constraints, and contrast-enhanced CT was used for metastatic assessment. Ultimately, definitive diagnosis relies on histopathological examination.

Accurate differentiation between primary seminal vesicle tumors, direct invasion from adjacent CRC, and distant metastasis is essential for appropriate staging and treatment selection. Primary seminal vesicle carcinoma is extremely rare and typically presents as an isolated seminal vesicle mass without evidence of a primary malignancy elsewhere. On computed tomography, it usually appears as a mildly enhanced parenchymal mass with a centrally low-density lesion[13]. In contrast, direct invasion from rectal cancer generally demonstrates disruption of the anterior rectal wall and obliteration of the fat plane between the rectum and seminal vesicles, reflecting contiguous tumor extension[14]. Metastatic lesions, however, are more likely to present as focal nodular masses with marked enhancement. In the present case, contrast-enhanced CT demonstrated a nodular markedly enhanced lesion in the seminal vesicle region with preservation of the fat plane between the rectosigmoid tumor and the seminal vesicle. Intraoperative exploration further confirmed the absence of direct seminal vesicle involvement. Histopathological examination revealed adenocarcinoma infiltrating the stromal and muscular layers of the seminal vesicle with morphology similar to that of the primary colorectal tumor. Although immunohistochemical analysis was not performed, the integration of imaging, intraoperative, and histopathological findings supported the diagnosis of distant seminal vesicle metastasis from rectosigmoid adenocarcinoma.

Due to the rarity of seminal vesicle metastasis, standardized treatment strategies have not yet been established. Available literature suggests that surgical resection remains the primary treatment option when complete removal of both the primary tumor and metastatic lesion can be achieved[15]. However, there is controversy in the academic community concerning the application of radiotherapy to the seminal vesicle surgical area. Although evidence specific to CRC with seminal vesicle metastasis is lacking, some studies in prostate cancer with seminal vesicle involvement suggest a potential role for adjuvant radiotherapy in selected patients[16]. However, the potential side effects of pelvic radiotherapy, such as urinary frequency, urgency, difficulty urinating, or bladder irritative symptoms, and the potential impact on fertility and sexual function must be carefully considered.

Patients with rectosigmoid cancer and seminal vesicle metastasis, according to current guidelines, are classified as having metastatic CRC. In an oligometastatic state, the treatment goal is to eradicate all visible metastatic foci through local intervention to prolong survival and achieve a potential cure. If treatment of both the primary lesion and the metastatic lesion in the seminal vesicle can be surgically achieved with R0 resection (i.e., negative pathological margins), surgical resection should be the preferred local treatment, supplemented by postoperative systemic adjuvant chemotherapy to eliminate micrometastases and reduce the risk of recurrence[17]. Conversely, when distant metastasis is present, the potential risk of bone marrow suppression from radiation therapy may affect the tolerability of subsequent chemotherapy, making it a less favorable initial treatment choice[10]. Treatment strategies should prioritize systemic therapy aimed at controlling stage IV disease.

Although a few studies have reported patients with CRC with distant metastasis to the seminal vesicles, these cases were observed postoperatively (Table 1)[1,9,11]. In contrast, this study documents a rare case of synchronous metastasis accompanied by comprehensive treatment and follow-up records, offering a novel perspective for clinical practice. Future investigations should focus on delving deeper into the pathogenesis and treatment strategies of such rare metastasis patterns to optimize prognosis and enhance quality of life. Moreover, establishing multicenter collaborations to gather extensive case data is important for the development of more precise treatment guidelines.

Table 1 Overview of the clinical characteristics and treatment outcomes of patients with colorectal cancer with seminal vesicle metastasis.

Ref.	Primary tumor location	Site of metastasis	Timing of metastasis	Metastasis therapy	Survival status
Arenas Hoyos et al[1]	Transverse colon	Left seminal vesicle	6 years postoperatively	6 cycles of FOLFIRI + panitumumab	Death at 3 months
Hsu et al[9]	Ascending colon	Right seminal vesicle	3 years postoperatively	Metastasectomy + systemic therapy	NR
Atici et al[11]	Descending colon	Left seminal vesicle	15 months postoperatively	Metastasectomy	NR
Current case	Rectosigmoid junction	Right seminal vesicle	Synchronous	Synchronous colon resection and metastasectomy + 12 cycles of mFOLFOX6	NED at 2 years

This table summarizes relevant clinical data from selected publications and the current study regarding primary colorectal tumors with metastases. NR: Not reported; NED: No evidence of disease.

CONCLUSION

Seminal vesicle metastasis from CRC is extremely rare and poses diagnostic challenges. Early recognition, accurate differentiation, and comprehensive treatment may improve patient outcomes.

ACKNOWLEDGEMENTS

The authors thank the patient for providing consent for publication of this case report.