Rare Case: Colorectal Cancer Spreads to the Urethra
Colorectal cancer is one of the most common types of cancer worldwide. When it spreads (metastasizes), it typically follows well-established pathways, most often to the liver, lungs, or peritoneum. However, a recent report by a team of Australian doctors, published in medical literature, describes an exceptionally rare case in which colorectal cancer spread to the urethra (the tube that carries urine out of the body).
The authors of the report “A rare case of urethral metastasis from colonic origin” are Faiyaz Rahman, Shravankrishna Ananthapadmanabhan, Jeremy Saad, Bishoy Hanna, Isaac Thangasamy, and Celalettin Varol.
The case began when a 78-year-old patient sought help from a urologist due to worsening urinary difficulties that eventually led to complete urinary retention. His medical history was complex: he had previously been treated for an enlarged prostate, as well as rectal cancer (the final part of the large intestine), which had already metastasized to his liver and lungs. He was undergoing palliative chemotherapy at the time.
During a cystoscopy, a procedure that allows doctors to examine the inside of the urinary tract using a small camera, an unexpected finding emerged. A papillary tumor was discovered, completely obstructing the urethra. Urethral tumors themselves are extremely rare, accounting for less than 1% of all urinary tract cancers. Even more uncommon are secondary urethral tumors, those that spread from another organ. When they do occur, they typically originate from nearby structures such as the bladder or prostate.
Only about a dozen similar reports have been documented in medical literature since 2000
To determine the origin of this unusual tumor, pathologists used immunohistochemistry, a technique that identifies specific proteins (markers) on the surface of cells.
Cancer cells from the urinary tract typically express a protein called CK7, whereas colorectal cancer cells do not. Conversely, the protein CK20 is found in both types. Analysis of the tumor in this patient’s urethra revealed that it was CK7-negative and CK20-positive. In addition, it tested positive for CDX2, a marker characteristic of intestinal cells. The conclusion was clear: these were colorectal cancer cells that had somehow spread to the urethra. As the disease progressed further with additional metastatic deposits, the medical team decided to transition to supportive end-of-life care. Given the extreme rarity of such cases, only about a dozen similar reports have been documented in medical literature since 2000; each new case provides valuable insight.
This unusual case highlights an important lesson for the medical community
Treating such rare metastases is particularly challenging due to the lack of standardized guidelines. In this case, because the cancer was already advanced, a palliative approach was chosen. The urethral tumor was partially removed to relieve urinary obstruction, and a catheter was placed to assist the patient, alongside continued chemotherapy aimed at controlling disease progression.
This unusual case highlights an important lesson for the medical community: cancer can behave unpredictably. When a patient with a history of cancer, even one not typically associated with the urinary system, develops new symptoms such as difficulty urinating or blood in the urine, these should not automatically be attributed to common conditions like an enlarged prostate.
As the authors concluded, this case serves as a reminder that maintaining a high index of suspicion and promptly investigating new urinary symptoms in patients with known colorectal cancer can lead to earlier detection and more timely management, potentially improving both outcomes and quality of life.
Image: Baylor College of Medicine; Get screened for colon cancer for prevention, early diagnosis
