LAUSR

Rectal carcinoma metastasis to the penis is extremely rare. Fewer than 40 cases have been reported worldwide. This paper describes the diagnosis and treatment of a patient with isolated metastasis to the penis 33 months after Miles surgery for rectal cancer. In combination with the available literature, the metastasis mechanism, treatment options and the prognosis of the patient are discussed. The patient, a 66-year-old male, underwent laparoscopic Miles surgery for rectal cancer at Xuzhou Medical University 4 years ago. The histopathological examination revealed a moderately differentiated adenocarcinoma of the rectum. The patient underwent six cycles of XELOX chemotherapy after surgery. Regular followup examinations of tumour markers and abdominal computed tomography (CT) examinations showed no abnormalities. One year ago, another abdominal CT examination showed a lump in the corpus cavernosum on the right, as shown in Figure 1. The patient subsequently attended our hospital for treatment. Physical examination of the patient showed that he was generally in good condition and the penis was normal in appearance. Routine blood biochemistry and tumour markers were in the normal range. A further positron emission tomography–CT scan at our hospital demonstrated a hypermetabolic mass at the base of his penile shaft; the presence of other metastatic sites was excluded, as shown in Figure 2. A needle biopsy of the penile mass was performed under ultrasound guidance. Immunohistochemistry examination revealed small focal atypical glands and rectal adenocarcinoma metastasis to the penis was considered. Total penectomy and urethroperineostomy were performed by a urological surgeon at our hospital 11 months ago. Immunohistochemistry of the penile lump revealed a moderately differentiated adenocarcinoma consistent with primary rectal carcinoma, as shown in Figure 3. The patient’s post-operative recovery was good. The patient underwent six cycles of a capecitabine single-drug chemotherapy regimen. To date, there has been no tumour recurrence or metastasis. In penile metastasis, the primary tumour usually originates from malignant tumours of the urinary system. For cases of rectal cancer involvement of the penis after radical surgery, it is currently believed that the most likely mechanism underlying metastasis to the penis is retrograde venous spread, where the tumour cells spread to the pudendal venous plexus in the direction of reverse venous return and then metastasize to the penis. Tumour cells can also transfer through direct invasion, or via the peripheral nerve or retrograde lymphatic pathways to the penis, leading to simultaneous penis metastasis. In this case, the isolated metastasis to the penis occurred nearly 3 years after Miles surgery for rectal cancer, and the possibility of a retrograde venous mechanism is high. The common clinical manifestations of rectal cancer involvement of the penis include urethral obstruction, pain, ulcers and priapism, among others. Few cases exhibit asymptomatic penile lumps or nodules. This patient had no chief complaint of discomfort; the penile mass was found by accident during imaging follow-up.