Urachal cancer is a rare malignancy originating from the urachus, a structure present during fetal development. This vestigial tissue is a remnant of the tube connecting the fetal bladder to the umbilical cord. Accounting for a small fraction of all bladder malignancies, this cancer typically arises in the dome of the bladder or along the urachal ligament toward the abdominal wall.
Understanding Urachal Cancer: Origin and Presentation
The urachus is an embryological structure that normally involutes after birth, forming the median umbilical ligament. This fibrous cord runs from the bladder’s apex to the umbilicus, but remnants of its lining can persist into adulthood. Urachal cancer develops when these remnants undergo malignant transformation. The vast majority of these tumors (about 90%) are adenocarcinomas, which are histologically similar to tumors found in the colon, often having a mucinous appearance.
Urachal tumors typically start deep within the bladder wall and grow outward into the surrounding fat and abdominal cavity. This location at the dome or apex of the bladder distinguishes it from the more common urothelial carcinoma. Since the tumor grows outside the bladder lumen first, symptoms often appear late, contributing to a poor prognosis. The median age at diagnosis is around 52 years, which is younger than non-urachal adenocarcinomas.
The most frequent initial symptom is painless blood in the urine (hematuria), which occurs when the tumor penetrates the bladder wall. Other non-specific symptoms include abdominal pain, urinary frequency, and dysuria. A rare but specific sign is the discharge of mucus from the urethra or umbilicus (mucinuria). The delayed onset of noticeable symptoms often results in diagnosis when the disease is already locally advanced or has metastasized.
Identifying the Disease: Diagnostic Methods
Diagnosing urachal cancer involves imaging, endoscopic evaluation, and tissue confirmation to differentiate it from other bladder tumors and determine the extent of spread. Cross-sectional imaging, such as Computed Tomography (CT) scans and Magnetic Resonance Imaging (MRI), is used to visualize the mass and check for metastasis. On a CT scan, urachal carcinoma characteristically presents as a midline mass, anterior and superior to the bladder dome. Calcifications are often displayed in 50% to 70% of cases, making a calcified supravesical mass in the midline highly suggestive of this cancer type.
MRI is beneficial because its multiplane imaging capabilities help evaluate the tumor’s local extension and involvement with adjacent structures. Cystoscopy, where a camera is inserted into the bladder, is performed to visually inspect the bladder lining and identify the tumor at the dome. This procedure evaluates if the carcinoma has penetrated the surface urothelium.
A transurethral biopsy is necessary to obtain a tissue sample to confirm the diagnosis of adenocarcinoma and rule out primary bladder cancer. Diagnosis is supported by finding a tumor localized to the bladder dome, an absence of widespread glandular changes in the rest of the bladder, and confirmation that the cancer did not originate elsewhere. Staging the disease, often using systems like the Sheldon or Mayo systems, is accomplished through imaging to guide treatment and predict prognosis.
Treatment Strategies
The only potential for cure in non-metastatic urachal cancer is achieved through aggressive surgical removal. Treatment is primarily surgical, focusing on achieving a complete resection with clear margins. This procedure is known as an en bloc resection, designed to remove the entire path of the urachus and the tumor as a single specimen.
The required surgery involves a partial cystectomy, removing the dome of the bladder containing the tumor. To ensure all potentially cancerous urachal tissue is excised, the procedure also necessitates the removal of the urachal ligament, surrounding soft tissue, and the umbilicus. This extensive removal is necessary because the tumor tends to spread locally along the urachal tract. If clear surgical margins cannot be achieved with a partial removal, a more extensive radical cystectomy may be required.
The role of additional treatments, such as chemotherapy or radiation, is not yet standardized and is often reserved for advanced or metastatic disease. Chemotherapy regimens often include agents like 5-fluorouracil and cisplatin, due to the tumor’s similarity to colorectal cancer. Adjuvant therapy may be considered depending on the tumor stage and grade, especially if surgical margins are positive or if there is lymph node involvement.
Prognosis and Follow-Up Care
Prognosis for urachal cancer is significantly influenced by the stage of the disease at diagnosis and the status of the surgical margins. Localized disease carries a much better outlook, with five-year overall survival rates around 50% to 70% for early-stage cases. However, the median overall survival drops substantially for patients with advanced disease (Stage III or above). The Sheldon staging system, which classifies the cancer based on the depth of invasion, is commonly used to determine prognosis.
Other factors influencing the long-term outlook include the tumor’s grade and the presence of positive lymph nodes. A positive surgical margin, indicating incomplete tumor removal, is associated with a higher risk of recurrence and a poorer survival rate. Due to the high risk of local recurrence and metastasis, long-term surveillance is mandatory for all patients.
Follow-up typically includes regular imaging, such as CT or MRI scans, to monitor for recurrence in the pelvis or distant sites. Periodic cystoscopies may also be performed to check the remaining bladder for local recurrence. The monitoring schedule is usually intense in the first few years after surgery and then gradually decreases over time.