Penile cancer spreads in a predictable, stepwise pattern through the lymphatic system. It first reaches the inguinal (groin) lymph nodes, then moves to the pelvic lymph nodes, and only in late-stage disease does it travel to distant organs like the lungs, liver, bone, or brain. About 2.2% of patients have distant spread at the time of diagnosis, making it uncommon but serious when it occurs.
The Groin Lymph Nodes Are the First Stop
The lymphatic vessels draining the penis lead directly to the inguinal lymph nodes, which sit in the crease where your thigh meets your torso. Up to 45% of penile cancer cases involve these nodes, making them by far the most common site of spread. When penile cancer metastasizes here, the nodes often swell into firm lumps you can feel under the skin. Healthy lymph nodes are about the size of a bean and usually aren’t noticeable, so any persistent swelling in the groin area is a key warning sign.
Spread to the groin typically starts on one side before involving both sides. In staging terms, a single swollen and movable groin node on one side represents earlier-stage spread, while involvement of multiple nodes or both sides indicates more advanced regional disease.
Pelvic Lymph Nodes Come Next
There are no direct lymphatic channels connecting the penis to the pelvic lymph nodes. Cancer only reaches the pelvis after first passing through the groin nodes. This is why doctors don’t surgically evaluate pelvic nodes unless the groin nodes already contain cancer. When at least two superficial groin nodes are affected, the chance of pelvic node involvement jumps to between 23% and 56%. Pelvic lymph node spread is harder to detect by physical exam alone since these nodes sit deep inside the body, so imaging is needed to identify them.
Distant Organs: Lung, Liver, Bone, Brain
Spread beyond the lymph nodes to distant organs is rare and happens late in the disease course. When it does occur, the most commonly affected sites are the lungs, liver, bones, and brain. Only about 2.2% of penile cancer patients have detectable distant metastasis at diagnosis. The prognosis at this point is significantly worse: the five-year survival rate for distant-stage disease is roughly 10%, compared to 79% for cancer that remains localized to the penis and 57% for cancer that has spread to regional lymph nodes.
Survival rates for patients with confirmed distant spread are sobering. One-year survival sits at about 35%, dropping to 17% at three years and 13% at five years.
What Makes Spread More Likely
Not all penile cancers carry the same risk of spreading. A systematic review of prognostic factors identified several features of the primary tumor that predict whether cancer has reached the lymph nodes. The strongest predictor is lymphovascular invasion, meaning cancer cells have entered the small blood or lymphatic vessels within the tumor. Tumor grade also matters: moderately differentiated tumors carry about 2.6 times the odds of lymph node spread compared to well-differentiated tumors, and poorly differentiated or aggressive subtypes raise the odds to about 3.3 times.
Depth of invasion plays a significant role too. Among patients whose tumors measured 5 mm deep or less, 90% did not have lymph node metastasis. Once tumors grew deeper than 5 mm, nearly half had spread to the nodes. Perineural invasion, where cancer grows along nerve fibers, is another red flag: about 73.5% of patients with this feature had groin node involvement, compared to just 24.4% without it. Younger age at diagnosis was also linked to higher metastatic risk, though this finding is less well understood.
How Spread Is Detected
MRI is considered the gold standard for evaluating the primary tumor and determining how deeply it has invaded local structures. It shows whether cancer has grown into the deeper erectile tissues or the urethra, which directly affects surgical planning. MRI is also used to evaluate lymph nodes in the groin and pelvis.
For patients with confirmed lymph node involvement, CT scans of the chest, abdomen, and pelvis are recommended to check for distant spread. CT is the preferred tool for spotting metastasis in the lungs, liver, and other organs. PET/CT scans, which highlight areas of high metabolic activity typical of cancer, offer strong accuracy for groin node assessment, with a sensitivity of about 88% and a specificity of 98%.
Dynamic sentinel lymph node biopsy is another option for patients whose groin nodes feel normal on physical exam but who have higher-risk tumors. This procedure identifies the first lymph node that drains from the tumor and tests it for cancer cells. It has a pooled sensitivity of about 87%, meaning it correctly identifies spread in the majority of cases, though a small percentage of positive nodes can be missed.
Why the Pattern of Spread Matters
The stepwise nature of penile cancer spread is actually useful from a treatment perspective. Because cancer reliably passes through the groin nodes before reaching anywhere else, catching and treating node involvement early can prevent further progression. If the groin nodes are clear, pelvic spread is essentially ruled out, and distant metastasis is extremely unlikely. This is why lymph node evaluation is one of the most critical parts of penile cancer staging, often determining the entire treatment approach and long-term outlook.