1 Background

When performing robotic-assisted radical prostatectomy (RARP) for prostate cancer (PCa), the first steps usually involve separating the anterior wall of the prostate from the pre-prostatic tissue (PPT). This allows to identify anatomical landmarks and safely start dissection. Generally, few attention is given to this tissue even if pelvic lymph node dissection (PLND) is associated. However, the rare involvement of PPT lymph nodes (LN) by PCa metastasis has already been reported by several authors in the literature and may influence the therapeutic strategy in intermediate and high-risk PCa patients [1,2,3,4,5,6,7]. We present the case of a 69-year-old man who underwent RARP with extended PLND (ePLND) for an aggressive localized PCa. The preoperative evaluation revealed a PPT nodule that was sampled during transrectal ultrasound-guided prostate biopsies and showed the same aggressive PCa histologic pattern as the prostate biopsy samples. Definitive histopathological analysis of operative specimen revealed a locally advanced aggressive PCa with extracapsular extension (ECE) and 8-mm size LN metastasis in a left pelvic LN and 23-mm size LN metastasis in a PPT LN. To our knowledge, few cases of PCa LN metastasis to PPT of this size have been reported in the current literature. We reviewed current literature and sought to report this case to share the particular images observed on preoperative imaging and to reinforce benefits of resecting PPT systematically for evaluation when performing PLND for PCa.

2 Case presentation

A 69-year-old man consulted our urology department for a raised serum prostate-specific antigen (PSA) level reaching 57 ng/mL. He reported familial history of PCa at the first degree. On physical examination, induration of left prostatic lobe was felt on digital rectal evaluation without palpable adenopathy. Transrectal ultrasonography showed hypoechogenic lesion in left prostatic lobe and an unusual supra-centimetric nodule localized in PPT. Pelvic magnetic resonance demonstrated two lesions in the prostate peripheral zone at the level of postero-basal and postero-apical segments (see Fig. 1). Additionally, a well-delimited nodule of 19 mm was seen on right paramedian side of PPT, suggesting a LN metastasis (see Fig. 1). Transrectal ultrasound-guided prostate biopsies were performed. On the left side, 2 biopsies out 6 showed a Gleason 10 prostatic adenocarcinoma. On the right side, all biopsies (9 out 9) showed Gleason 9 prostatic adenocarcinoma. The prostate capsule was not invaded. The PPT nodule which was also biopsied showed Gleason 9 prostatic adenocarcinoma. Prostate-specific membrane antigen (PSMA) positron emission tomography-computed tomography scan (PET-CT) was performed and revealed hypermetabolic expression of PSMA from the left prostatic lesion and the right para-median PPT nodule. Transperitoneal RARP with bilateral ePLND was performed and PPT was also resected and sent separately for evaluation. Histopathological evaluation of the operative specimen showed Gleason 9 locally advanced bilateral prostate adenocarcinoma with lymphovascular invasion and ECE (see Fig. 2). The base of the left seminal vesicle was invaded with positive surgical margin at the level of prostatic left posterior face. A PCa metastasis was found in 1 of the 20 retrieved pelvic LN (8mmn, left side) and a 23 mm LN metastasis was found in the PPT (see Fig. 2). Considering the results, adjuvant therapy (androgen deprivation therapy with external radiotherapy) was initiated.

Fig. 1
figure 1

Pelvis magnetic resonance imagery. A Round pre-prostatic nodule of 19 × 17 mm in anterior and right-paramedian position (T2 sequence, sagittal plane). B After Gadolinium administration, the nodule showed mild contrast-enhancement (T1 sequence, axial plane)

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Fig. 2
figure 2

PSMA PET-CT. PSMA PET-CT showed abnormal overexpression of PSMA-ligand from right-paramedian anterior nodule (15 mm) and left lobe of prostate (from base to apex) on transversal view (A) and coronal view (B). Mild overexpression was also observed from posterior face of prostate right lobe on sagittal view (C)

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3 Discussion

When performing radical prostatectomy for PCa, PLND is recommended in selected intermediate-risk patients and in all high-risk patients by current guidelines, as LN metastasis have negative influence on biochemical recurrence and survival rates in those patients [8]. The direct therapeutic impact of PLND remains debated as it is believed not to improve oncological outcomes including survival [9]. However, it is the most accurate and reliable staging method to detect PCa LN metastasis, which influences the postoperative therapeutic strategy [8, 9]. ePLND is the currently recommended pattern of PLND for intermediate and high-risk PCa as it allows adequate staging and prognostic evaluation in up to 94% of the patients [10]. Despite recent improvement, specific imaging methods such as PSMA PET-CT cannot replace the diagnostic contribution of ePLND yet [8]. ePLND involve removing the lymph nodes overlying the external iliac vessels, within the obturator fossa, and adjacent to the internal iliac artery. But when performing ePLND, little consideration is generally given to the pre-prostatic tissue/prostatic anterior fat pad which is not included in the template. Though, potential implication of this tissue in lymphatic spread of PCa has already been reported by several multicentric and large single-centre series [1,2,3,4,5,6,7,8]. LN are present in this tissue in up to 10.6% of time and harbour PCa metastasis in up to 1.3% of intermediate- and high-risk patients [1,2,3,4,5,6,7,8]. In their series of 197 patients, Kim et al. separated the anterior fatpad in three parts (left, middle, right) and found that patients had often LN in the middle one (89%), as is our case [6]. According to some authors, PPT LN metastasis can be found in patients without synchronous pelvic LN metastasis and this area might thus represent an independent landing zone of PCa metastasis, potentially inducing tumor upstaging after pathological analysis [8]. However, due to the rarity of LN metastasis in the PPT, indicators on which patients may benefit the most from PPT analysis remains unclear. Further, some surgeons might be reluctant to perform this procedure albeit it is not expensive, considering it may increase the operative time. Several authors tried to find clinical characteristics in patients with PCa metastasis in PPT LN [3,4,5,6,7]. Kwon et al. retrospectively analyzed 8800 patients from eleven international centers across three countries [4]. Eighty-eight patients had metastatic disease to PPT LN with sixty-three (71.6%) patients upstaged after pathological analysis. They also found that patients with LN metastasis in PPT, independently from pelvic LN status, had more aggressive PCa (higher incidence of biopsy Gleason score 8–10, pathologic N1 disease, ECE, or positive surgical margin). This is line with other reports and was also observed in our case [1,2,3, 5,6,7]. After reviewing current literature, several questions remain over the benefits of this procedure and the patients in which it should be performed considering the rarity of PCa nodal metastasis in PPT. In most studies, all patients underwent PPT removal or had synchronous pelvic LN metastasis indicating adjuvant therapy [1,2,3,4,5,6,7,8]. Jeong et al. reported no recurrence in 2-year follow-up of 3 patients out of 258 patients with only PPT LN metastasis but no pelvic LN metastasis [11]. Besides, Kim et al. reported that adjuvant radiotherapy and short-term anti-androgen therapy might be beneficial for PCa patients with LN metastasis in PPT [6]. However, publications on long-term follow-up of PCa patients with metastasis in PPT LN are lacking. Additional prospective studies comparing patients with or without PPT removal with longer follow-up are needed to establish the real benefits of this removal and its contribution to the prognostic and treatment of intermediate and high-risk PCa patients.

4 Conclusions

PPT resection is often not part of the routine procedure when performing RARP with ePLND for PCa.

However, this tissue might contain LN that can harbour PCa metastasis, independently from pelvic LN status. This can influence postoperative tumoral staging and indication for adjuvant therapy in some patients. Considering the very low morbidity of this procedure, its technical facility, and the absence of substantial additional costs, PPT should always been resected and sent apart from the ePLND material for histopathological analysis in intermediate and high-risk PCa.