Penile cancer is a rare disease, its precise etiology remains unclear, and its risk factors mainly include poor hygiene practices, redundant prepuce,, phimosis and long-term stimulation of smegma . Extramammary Paget’s disease is also a rare skin cancer that is mainly observed in the elderly, and it mostly occurs in the vulva and male genital organ; in clinic, it is usually misdiagnosed as dermatitis or eczema of scrotum, thus delaying treatment . The primary lesion is mainly treated by surgical resection, and the surgical resection scope depends on the tumor size, infiltration depth, and the involvements of penis and surrounding tissues; theoretically, negative incisal margin should be guaranteed .
Regional lymph node metastasis (LNM) or not, the metastasis degree, and radical resection are the determinants that affect its survival rate. Some research suggests that, the postoperative 5-year survival rate of patients with no regional LNM reaches as high as 95%-100%, while that reduces to 80% in the presence of a single inguinal LNM, to 50% in the presence of multiple inguinal LNM, and to 0% in the case of pelvic or peripheral LNM . Inguinal LNM is the first metastatic region of penile cancer and scrotal Paget’s disease, and about 20%-40% cases have LNM . It is indicated in research that, inguinal LND prior to PN3 stage LNM is of curative effect, which can cure about 80% micro-metastatic cases . Therefore, inguinal LND plays an important role in its treatment, which is a vital indicator that affects patient prognosis and survival rate . For patients with LNM upon preoperative physical examination or imaging examination, inguinal LND should be carried out aggressively. Additionally, for patients with no LNM but are at high risk of micro-metastasis (① low differentiation (grade G3 and above); ② stage T2 and above; ③ tumor with vascular and lymphatic infiltration), preventive inguinal LND is suggested . Numerous studies demonstrate that, compared with delayed LND, preventive bilateral LND enhances the survival rate of patients with impalpable inguinal lymph nodes [13–15].
However, research indicates that, the traditional open inguinal LND is linked with obvious complications, such as wound infection, skin necrosis, lymphocyst, and lymphedema; the incidence rate is over 50%, which has restricted its clinical application .
To reduce the incidence of complications, clinicians have performed various technical improvements, such as reservation of great saphenous vein, prevention of sartorius displacement, dynamic sentinel lymph node biopsy and improved LND, and reduction in the anatomic vision. Nonetheless, these improved techniques may omit micro-metastasis, which may lead to considerable false negative rate and endanger the oncologic control. Additionally, the postoperative complication rate remains high, which ranges from 26.7–38.9% [17–19].
To reduce the incidence of open radical LND without affecting oncologic outcomes, minimal-invasively technique of laparoscopic inguinal LND emerges. This technique was first reported by Bishoff et al. in 2003; in 2006, Tobias-Machado further developed and applied laparoscopic inguinal LND in clinic, and the 0% skin morbidity and 20% overall morbidity were reported . Since the introduction of VEIL, different institutions have shared their experience in using this technique, which suggest that VEIL is a safe and effective minimally-invasive method. Kumar et al.  compared the complications and oncologic outcomes between video endoscopy inguinal lymphadenectomy (VEIL) and open inguinal lymphadenectomy (OIL) in treating carcinoma of penis in males. Their results found that VEIL was an oncologically safe surgery, which was linked with rather low incidence (especially for leg swelling-related complications) and shortened length of stay. Russell et al.  retrospectively analyzed 34 patients with penile cancer undergoing endoscopic inguinal LND, analyzed and assessed the harvested lymph nodes, related perioperative indexes and postoperative complications. Their results discovered that, from the technical perspective, VEIL was feasible, and it was comparable to the open surgery in terms of the number of harvested lymph nodes. Importantly, compared with OIL, VEIL was advantageous in the reduced complication rate and rapid recovery. In our study, among those 11 patients receiving laparoscopic retrograde inguinal LND, (8.92士4.00) lymph nodes were harvested during left inguinal LND, while (8.54士5.04) lymph nodes were harvested in right inguinal LND; the patients were followed up for 2.5 to 19.5 months after surgery, and no tumor relapse or metastasis of primary lesion, inguinal or pelvic lymph node was reported.
Such results further proved the previously reported results, which verified the feasibility and safety of laparoscopic inguinal LND; besides, such technique achieved favorable oncologic control, with rapid recovery, few complication and short length of stay. The main reasons for this result are that, the small incision better preserve the skin blood supply; secondly, the tiny lymph vessels are amplified under laparoscope, which can be more thoroughly clamped, thus reducing the chance of lymph leakage; additionally, the incision is far away from major vessel, avoids sartorius translocation, and markedly reduces the surgical wound.
Through literature review, we found that, the trans-huckle subcutaneous approach VEIL is reported in almost all previous articles on laparoscopic inguinal LND, while the trans-hypogastrium subcutaneous approach VEIL is rarely reported. In the case of pelvic LNM of penile cancer or scrotal Paget’s disease that requires simultaneous inguinal and pelvic LND, the traditional trans-huckle subcutaneous approach VEIL requires to disinfect again and to change patient position and the position of Trocar placed, which will inevitably extend the surgical operation time. Therefore, we reported a novel trans-hypogastrium subcutaneous approach inguinal LND in this study, in which only 4 Trocar were necessary to be placed at the puncture points in the hypogastrium (2 cm at the lower umbilical margin, midpoint between umbilicus and pubis, midpoints between the left and right anterior superior iliac spines and the umbilicus) for bilateral inguinal LND. Besides, any change was not required in the case of pelvic LNM, instead, only the Trocar position inside the extraperitoneal space was necessary to carry out PLND through the same incision. Additionally, this surgical approach also possesses the following superiorities: (1) great operation space, clear surgical field, clear anatomical layer, convenient operation, and reduced possibility of intraoperative injury; (2) it thoroughly eliminates the inguinal lymphatic and fat tissues, accurately distinguishes the flap level, preserves blood vessels and lymphatic vessels to provide blood supply for flaps, and reduces the postoperative complications such as flap ischemic necrosis and lymphatic fistula; (3) it also substantially shortens the operation time required for changing the body position and skin preparation; (4) there is no puncture incision in the leg, which is more beautiful and can theoretically further reduce the incidence of lower limb wound complications.
Inguinal lymph nodes include superficial inguinal lymph nodes and deep inguinal lymph nodes, which are located at the upper and medial side of anterior femur. The superficial lymph nodes are located inside the superficial subcutaneous fascia, which are divided into the upper and lower subgroups, among which, the upper subgroup is arranged along the inguinal ligament, while the lower subgroup is arranged along the great saphenous vein. Moreover, the upper subgroup lymph nodes close to the medial side were closely related to urinary surgery, which are located near the great saphenous vein and receive lymph from the external genital and the perineum. The output tubes of superficial inguinal lymph nodes infuse the deep inguinal lymph nodes. The deep inguinal lymph nodes are located at the deep surface of fascia lata of the medial femoral vein, and they are arranged along the upper segments of femoral artery and femoral vein. Apart from receiving the output tubes of superficial inguinal lymph nodes, they also accept the lower limb deep lymphatic vessel, penis, scrotum, and lower anal lymphatic vessels. The output tubes of deep inguinal lymph nodes reach the extra-iliac lymph nodes upwards . Retrograde inguinal LND refers to dissection at the opposite direction of other genital neoplasm LNM, namely, the opposite direction of lymphatic return. Laparoscopic retrograde LND is advantageous in that, it further prevents tumor diffusion along the lymph due to surgical stress; moreover, retrograde operation is more aligned with the operation habit of the operator.
In addition, the trans-hypogastrium subcutaneous approach in this study is superior in that, it allows to directly and conveniently search for the femoral artery and vein and the great saphenous vein from the avascular area behind the adipose lymphatic tissue. When dissecting the superficial inguinal lymph nodes, the skin and great saphenous vein should be protected as far as possible; in the case of deep inguinal LND, the saphenous vein gap should be exposed in anatomical structure to expose the great saphenous vein. Any damage to the great saphenous vein during the surgery can lead to obstructed blood circulation, which may result in postoperative lower limb lymphedema and scrotal edema. Numerous studies suggested that [24–25], preservation of the great saphenous vein and its branch will not affect the thoroughness of LND; on the other hand, it reduces the postoperative complication rates such as incision infection, seroma and lower limb edema.
To avoid or recognize the early deep lymphatic damage and reduce the postoperative lymphatic system-related complications, the homemade real-time fluorescence lymph-mapping developer (indocyanine green) was applied in the latest one surgical patient in this study, which was simple and convenient in intraoperative operation, and allowed for lymphatic vessel visualization. Thus, it is promising to become the conventional tool for inguinal LND. However, randomized controlled trials with larger sample sizes are warranted to further verify the comparative study with the trans-huckle subcutaneous approach VEIL.